We're very close to the festival of Purim. It must be one of the most misunderstood Jewish holidays. People celebrate: some strictly adhere to the Talmudic commandment to get drunk until they can't tell the difference between "cursed be Haman" and "blessed be Mordechai," others organize costume contests, and still others go so far as to parade women to choose the prettiest... something unheard of in the values of Judaism...
The big question is: what are we celebrating? Obviously, everyone will answer that we are celebrating the miracle of the Jewish people's salvation from the clutches of Haman, the Persian minister who wanted to destroy them. Through Esther and Mordechai, along with the Jewish people's fasting and the Torah study of the children Mordechai gathered (24,000!), God performed a miracle, and what seemed to be the end was transformed into days of celebration and rejoicing.
This answer is correct, but it's the basic idea of Purim, what the story tells, but there's more to it.
Analyzing a verse from the Megillah, the Talmud extracts the true essence of Purim, which is the true source of the celebration. The Megillah states (Esther 9:27): “The Jews decreed and accepted upon themselves and their descendants […] to observe these two days […]”. The Talmud questions the meaning of the two expressions “decreeed” and “accepted”—wasn’t one sufficient? It offers the following explanation related to the Giving of the Torah (Shabbat 88a) (The parentheses are for explanation):
“'And they stood under the mountain' (this verse speaks of the moments before the Giving of the Torah at Mount Sinai), said Rav Avdimi bar Jama bar Jasa: this comes to teach us that God placed Mount [Sinai] upon them like a cone and said to them, 'If you receive the Torah, good, and if not, here will be your graves' (Because, if they did not accept, God would let the mountain fall upon the Jewish people!). Rav Acha bar Yaakov said: 'Hence we were forced to accept the Torah' (and it would not be a valid acceptance since it was induced by force, so we would be exempt from observing the Torah!). Rava said: 'In any case [we are obligated to observe it since] they accepted it again in the days of Ahasuerus (the Persian king of the Purim story), as it is written, 'The Jews established and accepted it,' that is, they established (i.e., confirmed in the time of Purim,) that which they had already accepted (at the time of the Giving of the Torah).”
From this passage in the Talmud, we see that the essence of Purim lies not only in the miracle itself, but also in the contribution of the Jewish people as a whole, which ultimately brought about the miracle. Their contribution was their willing acceptance of the Torah. Even if there had been any doubt about their obligation to God, during Purim the people dispelled all doubts and accepted the Torah, even though it meant destruction.
This leads us to understand that the true reason for the celebration is our connection with God. Purim celebrates the Jewish people's acceptance, even under threat of death, of connecting with God.
Today, the situation of the Jewish people is different in some aspects and similar in others. While we don't have a Haman trying to eradicate us from the earth (some say the president of Iran is Haman... in fact, Iran is the successor to Persia...), we have great difficulty connecting with God. This acceptance of the Torah is deeply ingrained in the soul of every Jew, but, in general, people are unaware of this choice. They go through life like everyone else, forgetting their own essence. Then, when some life situation shakes them up, they become aware that there must be something more to life than material pleasures and superficiality. At that moment, they are able to reveal that prior acceptance of the Torah. Purim celebrates this essential connection that transcends all barriers. It is there, but hidden, and it is the work of each individual to reveal it.
And just as in the time of Purim, that acceptance caused the miracle, may it be so for us too, that our will to connect to our own essence, to reveal our union with God, brings the greatest miracle, the coming of Messiah now!.