The Jewish festival of Passover is meant to celebrate the exodus of the Israelites out of slavery in Egypt. There is no real historical evidence for this event, but it is described in the Bible. According to the Bible, the Israelites were enslaved in Egypt and God sent plagues to punish the Egyptians and persuade them to let the Israelites go. One of those plagues was one in which the first born child of every household in Egypt would die. Israelites were told by God to sacrifice a lamb and and put the blood on their doorposts so that the angel of death would pass over their homes and kill only the children of the Egyptians. This is why the feast is known (in English) as Passover. It is celebrated as a sign of God's special favor towards the Jews.