Esther was a Jewish girl who had been taken captive. After her parents died, she was adopted a family member, Mordecai, who raised her as his own daughter.
King Xerxes was looking for a new queen. Many young women were considered, but after a year of beauty treatments, Esther was chosen to be the new queen.
Haman was the most powerful man in the kingdom besides the king. He was an evil man who hated the Jewish people and plotted to have them killed.
Mordecai persuaded Esther to go to the king and plead for the lives of the Jewish people. She could be killed for going before him when she hadn't been called. But she was brave and went to see the king. She invited him and the evil man, Haman, to a banquet. During the meal, she revealed the plot against the Jews and accused Haman. Haman was hanged on the gallows he had prepared for Mordecai, and the Jews were allowed to defend themselves. Mordecai was honored.
Since that time Jews have remembered Esther and celebrated the Feast of Purim.