Answer:
Passover commemorates the Jews being freed from Egypt. God helped free the Jews by inflicting ten plagues on the Egyptians. God told the Jews to mark their doors with lamb's blood and He would then pass over these homes, hence the term "Passover". On Passover, Jewish families get together and have a dinner called "seder" (pronounced sayder). It involves prayers, and Jews are not allowed to eat anything fermented, for example, breads (we eat Matzo instead). Orthodox Jews have a lot more involved.