The annual Jewish celebration of Purim is based on the so called "Book of Esther" which is not part of the Bible.

From Wikipedia

Esther is described in the Book of Esther as a Jewish queen of the Persian king Ahasuerus (commonly identified as Xerxes I, reigned 486–465 BCE). In the narrative, Ahasuerus seeks a new wife after his queen, Vashti, refuses to obey him, and Esther is chosen for her beauty. The king's chief advisor, Haman, is offended by Esther's cousin and guardian, Mordecai, and gets permission from the king to have all the Jews in the kingdom killed. Esther foils the plan, and wins permission from the king for the Jews to kill their enemies, and they do so. Her story is the traditional basis for Purim, which is celebrated on the date given in the story for when Haman's order was to go into effect, which is the same day that the Jews killed their enemies after the plan was reversed.

From the teachings of Kabbalah

According to the Book of Esther, the Royal Vizier of the king of Persia, whose name was Haman, had planned to kill of all the the Israelite in that country, ruled by the king Ahasuerus (Achashverosh in Hebrew), which is also presumed to have been Artaxerxes (or Xerxes for short), therefore Mordecai, who was an Israeli, and had a cousin named Esther which was also adopted by him as his daughter, married her to the King in order to foil Haman's plan.

This they accomplished, due, mainly, to the great unification and prayers of all the Israelite at that time in Persia, showing all of us what the unity of purpose can accomplish when done by an entire nation.  Thus the need for unity of purpose in anything that we want to accomplish.

But also viewed from Rav Berg's point of view, it had to do with the proper timing.

According to Rav Berg, it had to do with the ruling planet of Adar (Pisces) which also rules Kislev (Sagittarius). Purim, which occurs during the month of Adar, ruled by the planet Jupiter, and Chanukah, which occurs during the month of Kislev ruled also by the planet Jupiter, which is the planet with a genetic code  that connects to the consciousness of miracles, making it the channel to reveal the miracles of Chanukah and Purim.  Thus these events were planned to occur during these two months and under Jupiter's influence.

He tells us that in the Book of Formation, Abraham the Patriarch connected the month of Adar which means "special" or "unusual" with the astrological sign of Pisces.  Thus, Purim commemorates with happiness the fall of Haman. And at Chanukah we celebrate a similar event, the victory of the Maccabim over the Greeks.

But he claims that we do not say that once Kislev arrives we dwell in happiness.

There must be another explanation, he claims; and then he goes to connect it with the prayer of the Ana Beckoach. The prayer, as Kabbalists' students know, consist of 42 words or seven verses of six words each. It describes the creation of the Universe and everything that occurs within it.  This information is embodied specifically in the first letters of each word, as a sequence of 42 Aramaic letters.  All of creation, all of the stars and astrological signs, all that we encounter each day is expressed in this one prayer, specifically in these 42 letters. The seven stars or planets that influence our daily life are connected to to the seven verses of this prayer. The second verse in the Ana Beckoach refers to the planet Jupiter, which controls the month of Adar.

This verse contains a secret: its chain letters spells out the words Krah Satan, which means to tear away the Satan ( which is translated as the "Opponent", our own negative tendencies) and they are connected to the month of Adar, as described by Abraham the Patriarch. Only through this combination of letters can we even dream of gaining control over our lives. Yet the combination works only during the months of Adar and Kislev, which are controlled by the planet Jupiter. This revelation starts on the eve of the first day of the month of Adar and this is the seed level which is the strongest aspect of any process.

In the month of Adar there is an opportunity to exit the chaos that characterizes our lives today and replace it with control of that chaos.  Control in Kabbalah means complete removal of the chaos from our lives. It means controlling our destiny in a manner that will fill our lives with happiness and health, instead of sorrow and pain.

Historically, at Chanukah and Purim, a small group of people stood up to big empires and won. At Purim the Israelite were destined to be destroyed by Haman, the second in command to the king of Persia. But in the end, it was Haman who was destroyed. It is important to note that the victory did not take place because the enemy was attacked and defeated by an army, because according to Kabbalah the real enemy is only in consciousness. As with the  war against the Greeks at Chanukah, the outcome was not decided on the battlefield. Instead, the war was against negative consciousness: the desire to receive for the self alone.

Haman was defeated because Haman's consciousness was defeated. How was that possible? Kabbalah teaches that a special battle strategy was successfully used at Purim against the root cause of chaos, which is the thing that causes all physical or spiritual sickness, against the thing that brings destruction of marriages and the failure of businesses. This is the mother of all wars: the Armageddon war between the consciousness of the Light and the desire to receive for the self alone. Kabbalah teaches that in the age of Aquarius there will be a war of consciousness, because in this era we will understand that we must attack chaos at its source. The source is the desire to receive for the self alone.

Is it possible to make fulfillment of our inner desires our reality and to end all pain and suffering? There are many superficial ways in which we can make ourselves happy, but once the bank manager calls and informs us about problems with our cash flow, all that happiness dissipates. How can we prevent these kind of telephone calls?  How can we prevent sorrow, lack and pain in our lives? How can we fortify the drops of happiness spread throughout our lives and make them the dominant and continual reality of it? Only with the Krah Satan in the month of Adar.

Even though both holidays occur under the same Astrological influence, there is an important difference between them, at Chanukah a very small group of people created the miracle, while at Purim all the Israelite participated in the fast that Esther asked them to participate in, and they brought about the cancellation of Haman's consciousness.  They were united in one purpose, a purpose that agreed with the desires and the plans of our Creator.

When Mordechai returned from Jerusalem, it is written that he brought with him all the wisdom of Kabbalah, all the letter combinations and all the holy names. He brought the system by which we can destroy negative consciousness. Mordechai and Esther, with the cooperation of all the Israelite, erased negative consciousness from people's mind. Only in this way were they able to defeat Haman and everything that Haman represented. That is why both the Talmud and the Zohar state that in the time of the Messiah, the only holiday that would be celebrated will be Purim, by manifesting the energy of Krah Satan, in the month of Adar, with which we have the opportunity to establish the power of immortality and to connect with the energy of the Messiah.

The Shabbath before Purim has a hidden aspect even though most people are not aware of it and do not give much importance to it. It is the reading of the portion of Zahor in addition to the regular reading. There is something special about this reading, and Rav Berg taught us that it is very important for women and children to participate and listen to it. This is not said about any other reading.

Women, we learn from Kabbalah, have more positive energy than men. Only women, for example, have had sufficient energy to bear children, which gives them the ability to connect with the portion of Zahor that is exceedingly positive in comparison with all other Torah portions. That is the story of Amalek, which teaches us how to use our antidote against doubt. We activate certainty within ourselves by listening to this reading so that we can harness the energy of certainty in our battle in the removal of doubt. What is the source of this power and what is the connection to the holiday of Purim? Rav Berg tells us that this portion appears in the Torah at the end of two portions, Beshalah and Ki Tavo, in the first one, appears the secret of the awesome power of the 72 names of God and the miracle of the splitting of the Red Sea. Now, we know that after they performed this great miracle, they fell back into the consciousness of doubt. This is because they failed to continue living in the present and returned to the consciousness of the illusion of an imagined future and thus the illusory consciousness of uncertainty and the anxiousness of an unknown future.  Fear is the handcuff that binds us to the illusion of the future and disconnects us from the present. If we truly connect to the present we will have no doubts about any future, because according to the law of cause and effect, the present dictates the future.

The fruits of the tree of Knowledge of Good and Evil represent illusory consciousness. The serpent did nothing but to plant the seed of doubt in Eve. The serpent convinced her to exchange the consciousness of the true spiritual reality for the illusory consciousness of the physical world, and as Eve chose that illusion, she made the physical world and actuality.

And as a result of not practicing restrictions, they fell to uncertainty, illusion and doubt.  But what is the connection of all that and Purim, to the reading of the portion of Zahor and the spiritual force revealed in the Universe this day?

At Purim it is read the Book of Esther (Megilat Esther), which means the revelation (megilat) of the concealed (Esther), thus in Purim there is a revelation of the concealed because the Light of Chochmah is then revealed, and it removes doubt, chaos and any manifestation of negative energy in the Universe. Therefore when Mordechai and Esther, together with all the Israelite connected to this power over 2,800 years ago, they created the miracle of Purim.  And now, we do not celebrate Purim to commemorate that happening, but rather because of the energy that created that miracle is available on the 13th day of Adar and we receive immediate certainty and blessings, even more than those we receive in Yom Kipur.

Since Kabbalah teaches us that by removing doubt and uncertainty we can banish Chaos from the World, and this is exactly what occurs on Purim with the removal of the veil from the emanation of Chochmah, we can connect to the Light and all the abundance that it brings.

Therefore in the times of the Messiah, when the consciousness is akin to the one in Purim, with the veil of Chochmah removed and facing the real World instead of the Illusory one, the illusory stories of the Torah would be needed no more, and we will remain in the state in which our consciousness is during the Holiday of Purim.

Therefore we can say that we may have a taste of the World to come in Purim. The way to remove doubt is described in the portion of Zahor, when Moses, Aaron and Chor connected to the inner force of the letter Bet and established the system of the three columns in the spiritual work. By practicing "restriction", by caring for others and loving our neighbors as ourselves, it is possible to gain blessings and certainty. Any description of the future that contains any negativity is necessarily a description of an illusion.

The concept of "parallel  realities", or two worlds, one of illusion and one of truth, answers many questions.  We can transfer between the two worlds, just as we transfer between programs working simultaneously in the computer. The illusory world was created just to allow us to remove "Bread of Shame" and only after we practice restriction in this illusory world can we taste of the true world. If we stop and give up, we fall back into the illusory world.

Science already knows about the true world, and most of us have that knowledge already, but we all need to be done with the illusory world in order to bring about the true world.  We have to practice restriction, but we also need to work with the members of our environment, because in reality we are part of the cosmic totality and must have the desire to help all other aspects of the universe, in order to achieve completeness.

Of all the holidays only Purim emphasizes this need to become all one with others and to become our true selves, we may wear masks, but only as a symbol of the unreality of our illusory world, where we carry on with our egos and forget the truth of the fact that we are all but one Unity and it is as such that we can achieve anything.
When we read the Book of Esther, we not only reveal the secrets hidden within it, but also we build a connection to a cosmic event that occurs,  according to the Ari, on this day alone. Only on Purim we can connect to the complete unity of the true world. On Purim we are required to make only a small effort: be happy and get drunk. And the drunker we get, the happier, also, and the stronger that the connection will be.  In order to free ourselves from our negativity, we need to free ourselves from the illusory world. And the best way to do it, is by getting drunk. This makes us to lose our mindful consciousness, which will remove the barrier that separates us from the cosmic consciousness.

Since in Purim the entire cosmos is illuminated with the consciousness of certainty, by getting drunk on this day we gain certainty for the entire year. Drunkenness is not recommended on any other day of the year, since only in Purim is the Universe filled with certainty.

Therefore we use two tools at the time of Purim, drunkenness and the reading of the Book of Esther, in whose lecture we will participate by saying, out of the 72 names of God, the name Chaf Hei Taf, which acts as a ray of light or a laser beam, every time that the name of Haman appears, as if we were sending rays of light and cancellation of his negativity, every time his name is mentioned.

At the time of the Purim miracle, complete love and caring existed among the Israelite, and we try to connect to that energy, today, as well. Kabbalah tells us that this connection can only be achieved through love and understanding of the thing to which we want to connect.  Knowing that at the base of our beings we are all one, helps us to unite ourselves with our other selves.

Mordecai had left with others the diaspora and had returned to Israel with many others, but he returned to Persia, once that he learned all the secrets of Kabbalah, to just overcome the negativity of Haman, which he accomplished in this one day of Purim. He had been with Daniel and others, they remained in Israel, but he came back and with the help of Esther who was in a high position, being the Queen of Persia, and all the Israelite there, they accomplished this deed. The light was then revealed.

And this is what we want that the light will be revealed in our consciousness and that of everyone else. Thus we celebrate Purim, not to remember a historical event, but to reproduce that historical event all throughout the World and bring the kind of Consciousness that we call the Messiah.

This is the importance of participating in this event and been very aware of why we are participating in it and what is it that we are trying to accomplish.

But also, we must recognize, that everything in this Illusory World depends on the returning our consciousness to that state of grace that can be created here, and that all other holidays, if we achieve our purpose on this one, would be unnecessary, because we would have achieved the removal of Chaos in the World and we will be able to return to the real world, the Garden of Eden, our Paradise lost in consciousness, the consciousness of illusion, of fear and depression, of the belief in the unreality of the past and the illusory future, we need to live in the ever present moment and in accordance with the plan for which we were created. This is what can be achieved in Purim, what more can we expect and should we work for?