Jews in Jerusalem began celebrating Purim on Sunday night, one day after the holiday began elsewhere. The holiday began with the public reading of Megillat (Book of Esther) throughout the city.
Purim festivities began on Saturday night, as can be seen in these pictures of the children in the Jewish community of Hevron in their Purim costumes. Jews worldwide celebrated the deliverance of the Jewish people from their oppressors in the ancient Persian Empire during the period after the destruction of the first Holy Temple in Jerusalem and before the second was built.
Celebrations began with the public reading of the Megillah. The book relates the story of Purim, in which a sequence of events led to a Jewish woman named Esther (Hadassah) being crowned queen in time to use her position to save her people from a genocidal decree.
Haman, the Persian minister who tried to destroy the Jews, drew lots (Purim, in Hebrew) in the capital city of Shushan to choose the day on which he would carry out his evil plan, and the holiday was named accordingly. However, Haman was hanged and the Jews found that no one rose against them on the day he had chosen, the fourteenth of Adar, so that day became a holiday instead.
The holiday is the only one to be described in the Bible that is not in the Five Books of Moses, and is considered a symbol of hope and redemption for all generations. According to the Talmud, Purim will continue to be celebrated even in Messianic times.
In Jerusalem, Purim is celebrated on the fifteenth of Adar, Sunday night and Monday this year, in accordance with the Rabbinic decision that cities that were walled in the days of Joshua, Moses' successor, celebrate the holiday a day after the rest of the Jewish world. This is to commemmorate the continuation of the Jews' successful defense in Shushan that lasted for another day.
The holiday is marked by other laws in addition to the Megillah reading. During the day, celebrants eat a festive meal and send prepared food items to each other by messenger, usually costumed children. The gifts of food must include two types of food to at least one other person and are intended to strengthen unity and friendship within the Jewish nation, in contrast to the genocidal decree issued by Haman, who referred to the Jews as “scattered and dispersed.”
Another way in which Purim is observed is by giving money to the poor in order to allow them to celebrate the holiday as well. Money must be distributed on the day of Purim itself to at least two people, and each needy person should be given enough to allow him to buy food for a Purim feast. Many charities do this for donors who contribute by telephone or online.
Many Jews also have the custom of dressing up on Purim, in reference to the “disguised” nature of the holiday. In the Purim story G-d's salvation is revealed through seemingly natural events and not through miracles that change the laws of nature. The children in Hevron enjoyed their celebration despite Arab rioting at the Cave of the Patriarchs there.
Wine is often consumed to symbolize joy on Purim, and the sages of the Talmud suggested drinking until one can no longer distinguish between the hero Mordechai and the villain Haman. However, there are rabbinic opinions stating that one can obtain the inability to distinguish through sleep instead of drink, and according to all opinions a person should not drink if doing so would cause them to sin.
Haman was a desecendant of Amalek, the tribe that attacked the Jews when they left Egypt while they were still weak from years of slavery. The Bible decreed that Amalek must be destroyed, but this commandment was not completed. Modern day Iran is the site of ancient Persia where the Purim story occurred.