Passover is one of the most important Jewish religious festivals. The Passover celebration begins on the evening of the 14th of Nisan (first month of the religious calendar, corresponding to March-April) and lasts seven days in Israel, eight days in the Diaspora (although Reform Jews observe a seven-day period).

Numerous theories have been advanced in explanation of Passover's original significance, which has become obscured by the association it later acquired with the Exodus. In pre-Mosaic times it may have been a spring festival only, but in its present observance as a celebration of deliverance from the yoke of Egypt, that significance has been practically forgotten.

Passover Seder

The Seder is the ceremonial evening meal which is conducted on the first evening of Passover in Israel and by Reform Jews, and on the first and second evenings by all other observant Jews in the Diaspora. The Passover seder is one of the most widely observed of all Jewish customs.

 In the Seder, various special dishes symbolizing the hardships of the Israelites during their bondage in Egypt are served. During the seder, a platter, called a Seder Plate, is a main part of the dinner, and it has on it all of the main symbols of Passover.

Throughout the period of Passover, Only unleavened bread (Matzah) may be eaten. Jewish law also requires that special sets of cooking utensils and dishes, uncontaminated by use during the rest of the year, be used throughout the festival.

http://www.judaica-guide.com/passover/