The Passover is also the story of the Exodus. It is a story about Moses, who, rather than be drowned as the Egyptian Pharaoh decreed all son should be, is sent floating down a river in a woven basket. He is saved by the pharaoh's daughter and taken into the royal family that would have had him killed. He is named Moses because it means "one who is pulled out."
Once Moses realizes his true origins, he is distressed to see the situation of his fellow Hebrews. He is unable to maintain his rage and kills a slave master when he sees him brutally mistreating a Hebrew slave. Moses flees and lives a quiet life as a shepard for 40 years.
Eventually Moses is called by the Hebrew God through a burning bush to lead his people out of Egypt to freedom. He approaches the Pharaoh and requests a three day leave for the Hebrew population to celebrate a feast, but the Pharaoh refuses.
To punish him, God brings down the infamous 10 plagues culminating in the slaying of Egyptian firstborns. In order to spare their children, Hebrew families marked their door frames with blood. The avenging angel, upon seeing this sign, would "pass over" the home.
In terror, the Egyptians demand the Pharaoh let the Hebrews leave, but, before they are safely away, the Pharaoh changes his mind. The army closes in on them when a miracle happens. The Red Sea parts, and Moses and his followers are able to safely cross. The sea comes back together, and the Egyptian forces drown. This tale is just the beginning. The Hebrews spend the next 40 years wandering the desert before reaching Canaan or the Land of Israel.
For a more information on the history of Passover, you can check out the History Channel's website, which also includes some videos on the holiday as well as an investigation of the historical aspect of this event.
