Passover is the first of the three major festivals with both historical and agricultural significance (the other two are Shavu'ot and Sukkot). Agriculturally, it represents the beginning of the harvest season in Israel, but little attention is paid to this aspect of the holiday. The primary observances of Pesach (PAY-sahch, with a "ch" as in the Scottish "loch") are related to the Exodus from Egypt after generations of slavery. Pesach means to pass through, to pass over, to exempt or to spare. It refers to the fact that G-d "passed over" the houses of the Jews when he was slaying the firstborn of Egypt. In English, the holiday is known as Passover. "Pesach" is also the name of the sacrificial offering (a lamb) that was made in the Temple on this holiday.
Probably the most significant observance related to Pesach involves the removal of chametz (leaven; sounds like "hum it's" with that Scottish ch) from our homes. This would include all sources of bread and bread products. This commemorates the fact that the Jews leaving Egypt were in a hurry, and did not have time to let their bread rise.
On the first and second nights of Pesach a special family meal is served filled with ritual to remind us of the significance of the holiday. This meal is called a seder, from a Hebrew root word meaning "order," because there is a specific set of information that must be discussed in a specific order. A book, called the Haggadah, is used to guide us with the order of the seder. The Haggadah was written as a teaching tool, to allow people at all levels to learn the significance of Pesach and its symbols. On each of these nights, the story of Passover is told, symbolic foods are eaten, a wonderful meal is served and lots of singing and stories are shared, all of which must be completed by midnight!
A favorite part of the meal is the hiding of the afikomen (a-fee-ko-men) - this piece of matzah set aside earlier is eaten as "desert," the last food of the meal. Different families have different traditions relating to the afikomen (a Greek word in the middle of a Hebrew feast, meaning "that which is coming", i.e. dessert). Some have the children hide it, while the parents have to either find it or ransom it back. Others have the parents hide it. The idea is to keep the children awake and attentive throughout the pre-meal proceedings, waiting for this part, but many of the adults get involved as well.