Jerusalem Talmud Megillah 1:5:3

The book of Esther is one of the five megillot (scrolls), part of the section of the Hebrew Bible called Writings. It tells the story of Esther, a Jew who becomes queen of Persia and together with her cousin, Mordekhai, foils a plot of the evil Haman to destroy the Jews. To commemorate the transformation from “grief and mourning to festive joy” (9:22), Esther and Mordekhai establish the holiday of Purim. The book of Esther is read publicly in the evening and morning of Purim.

Queen Esther is the protagonist of the book of Esther. She hid her Jewish identity after being chosen to marry the Persian king Ahashverosh and, along with her cousin Mordekhai, saved the Jewish people from the genocidal vizier, Haman.

Purim is a holiday commemorating the events of the book of Esther, where the Jewish Queen Esther and Mordekhai overturn a decree of genocide against the Jews of the ancient Persian Empire.