This evening (Monday), after the evening prayer and the reading of the Megillah pf Esther, Purim celebrations began with the reading of the Megillah, which tells the story of the miracle that saved the Jewish people during the time of Mordechai and Esther.
The holiday of Purim, the holiday of redemption and salvation, is the last of the holidays mentioned in the Bible and is considered a symbol of hope for redemption and salvation for generations. On Purim, Jews observe four commandments, all starting with the letter "M": Megillah reading, Mishloach Manot, Matanot Le'evyonim, and the Seudah (feast).
Megillah Reading - Jews read the Megillah twice on Purim, once at night and once during the day. The reading of the Megillah is essentially the proclamation of the great miracle that occurred for the Jewish people, and from it, their draw strength to remember the great miracle that God performed for His people Israel. Jews strengthen their faith in God's providence, His love, and reverence. After the Purim miracle, the Jewish people accepted the Torah anew with love, and Purim is a day of special significance for receiving the Torah with love in every generation.
Mishloach Manot - Jews send two portions of food to one another, to increase love and unity among the Jewish people. The remedy for Haman's decree and his accusation of a "scattered and divided" people is unity within Israel, as Esther said to Mordechai, "Go, gather all the Jews."
Matanot Le'evyonim - Jews give money or a meal allowance to the poor. In every celebration, Jews are commanded to always remember the poor and give to them, making them happy, and this is the true joy.
Seudah (Feast) - Jews hold a feast and banquet. On Purim, because the salvation of the Jewish people was a physical salvation, Jews specifically celebrate with a feast and banquet. A special emphasis is placed on drinking wine, as the miracle was brought about through a feast and wine, and so we also drink wine.
Another aspect of wine is that "when wine enters, secrets come out," and Purim, which is a redemption through natural means, reveals that everything in nature and all events are under God's supervision, and that ultimately everything is inherently good. On Purim, Jews reveal the inner goodness of things.