What historical event is the reason Purim is celebrated?

Purim commemorates the events recorded in the Book of Esther, where Queen Esther and her cousin Mordecai thwarted a plot by Haman, the royal vizier, to annihilate the Jewish people in ancient Persia. The celebration marks the deliverance of the Jews from this decree, highlighting themes of survival, bravery, and divine intervention. Festivities include reading the Megillah (Book of Esther), giving gifts, and feasting, symbolizing joy and gratitude for their salvation.