Passover, or Pesach in Hebrew, is an eight-day spring holiday that celebrates the Israelites' exodus from Egypt.
The main ritual of Passover is the seder, a carefully choreographed meal held on the first two evenings of the holiday (in Israel, and for most Reform Jews, there's only one seder, on the first night). The seder is designed to provoke questions from children and to provide an opportunity for telling the story of how the Israelites were redeemed from slavery and given the gift of the Torah.
Holiday descriptions provided by Kveller.com.