This year's Passover begins on sunset of Monday, April 18 and goes through Monday the 25th of April, 2011Incorporating the holiday meal, the Seder relives the enslavement and subsequent Exodus of the Children of Israel from Ancient Egypt through the words of the Haggadah, the drinking of Four Cups of Wine, the eating of matzot, and the eating of and reference to symbolic foods placed on the Passover Seder Plate.
In the following passage from exodus, the Hebrew word for feast is חג chag, meaning "festival, feast, festival-gathering, pilgrim-feast" from חָגַג chagag, "to hold a feast, hold a festival, make pilgrimage, keep a pilgrim-feast, celebrate, dance, stagger."
The Seder itself is based on the Biblical verse commanding Jews to retell the story of the Exodus from Egypt:
8 You shall tell your son on that day, 'It is because of what the LORD did for me when I came out of Egypt.' (Exodus 13:8 ESV)
The Seder is considered an integral aspect of Jewish faith and identity. As the Haggadah—which contains the complete Seder service—explains, without the Exodus, the Jews would still be slaves to the Egyptian Pharaoh and would never have realized their role as a nation. Therefore this is an occasion for much praise and thanksgiving to God. It is considered a mitzvah (commandment) to embellish one's retelling of the Exodus on this night. Often the Seder lasts into the early hours of the morning of the next day, as participants continue to learn Torah and talk about the events of the night and sing special Passover songs included in the Haggadah.