I was asked to write about Passover for those who don't know. (I hope no one is offended by any of this.) So this is a very basic explanation and not 100% accurate explanation about Passover. (For more detailed information please click here.)
Many many years ago, the Israelites were slaves in Egypt. G-d spoke to Moses in a burning bush and eventually he (along with his brother Aaron) went to ask Pharoah to "let my people go." Pharoah of course said no and so G-d unleashed ten plagues on the Egyptians. The final plague was the death of the first born where Jews marked their doors so their homes were "passed over" and their first born children lived. (Get it ... Passover ... passed over??) Pharoah was so upset that he finally said the Israelites could leave.
Now this was not exactly a full endorsement and rightly so, Moses was scared Pharoah would renig. So the Israelites left very quickly and didn't have enough time to let their bread rise. (In the end Pharoah did change his mind, sent his people out after them and G-d drowned them in a river.)
Passover is 8 days (7 if you are reform or live in Israel) where we remember the time when we were slaves and now that we are free. To remember, we are permitted to eat only certain foods on Passover (some people already keep it more strictly but I am explaining the basics here).
For me, we can't have what is called chametz. Basically, that means no grains, breads, pastas, etc. We eat lots of matzah in place of some of these items. It makes for interesting cooking/eating for 8 days.
Some other off limit items: corn; corn syrup; beans; peanuts; pizza; bread; pasta; waffles; pancakes; cakes; cupcakes; lasagna; etc. Just to be clear, some of these items have Kosher for Passover variations.
Like I said, this is a very basic explanation. If you have any questions please feel free to email me or leave a comment. I'll do my best to explain!