I might not be totally up on my Judaism but I do believe that Passover is the most important of the Jewish holidays. I've gathered from the Jewish people that I know that it involves spending an unacceptable amount of time with your family and eating things like milk, honey and bland, tasteless crackers (the kind you might eat if you had the stomach flu).
In Exodus 9, God tells the Israelites that their calendar starts like, NOW, and they should kick-start the new year by gorging themselves on lamb (gorging is generally how I wind down my year). They should roast it, head and all, and take some of the blood and mark their doorposts with it. They should do this so God can tell their houses apart from those of the Egyptians and "pass over" them when he goes on his killing spree of first-borns. "I will pass through the land of Egypt that night, and I will smite all the first-born in the land of Egypt, both man and beast" (Exo 12:12). This is where the term "Passover" comes from.
It's weird to me that God not only smites all first-born human children but also all first-born beasts. In the Bible, it specifically mentions cattle (again, a huge waste of beef) but I've got to assume that pets are included, too. It's so much sadder when animals die - remember that part in Gorillas in the Mist when the poachers decapitate Digit, the favourite male silverback of Dian Fossey (played by Sigourney Weaver)? I watched that movie non-stop when I was a kid and always cried when Fossey breaks down and is like, "They took his head! They took his head!" while her guide Sembagare holds her and cries silently (the only way I've ever seen black men cry in movies).
After I read this bit, I was hoping that I'd find out the deal behind the unleavened bread. No deal, unfortunately. God tells the Israelites that they have to eat unleavened bread for the first seven days of Passover and if they do eat leavened bread then they'll be cut of from Israel. And he's intense about it. He repeats this rule almost verbatim in the same passage.
Following the first-born slaughter, the Israelites are led out of Egypt by Moses and Aaron and of course, the Pharaoh changes his mind and goes in hot pursuit of them. In the form of a "pillar of cloud" or, in modern vernacular, a "smoke monster," God leads the whole lot of them toward the Red Sea. We know what's about to go down. God gives Moses the power to part the Red Sea but -- and I don't know if it's ever really emphasized -- also the power to make it all come crashing down, killing all the Egyptians, which he makes good use of. And so the heartwarming story of Passover ends: "Thus the Lord saved Israel that day from the hand of the Egyptians; and Israel saw the Egyptians dead along the seashore" (Exo 14:30). Amazing.