Though Purim is a minor holiday on the Jewish calendar, it is widely observed and a favorite of children. According to the scroll of Esther 9:22, we are to observe Purim as a time of “feasting and gladness.” The holiday is marked not only the by reading of the scroll, but by Purim plays (spiels) and the wearing of costumes. A festive meal is eaten (se’udah) on Purim afternoon. These led to the rise of carnivals, incorporating these traditions and often adding games for children. In Israel, Purim is joyfully observed by parades and people of all ages dressed in costumes.
(From ReformJudaism.org, read more on their website.)