Before detailing the laws of the Seder, let us briefly survey the mitzvot we fulfill on the Seder night.
Two elements constitute the foci of the Seder: The first is commemoration of our Exodus from Egypt and emancipation from slavery and reflection on the significance of Israel’s freedom. The second is to transmit our tradition to the next generation. Both of these are included in the Torah’s commandment to tell the story of the Exodus on the night of the 15th of Nisan.
In order to make this commemoration tangible, the Torah commands us to eat the korban Pesaḥ (Paschal sacrifice), matza, and maror on this night. The Paschal sacrifice recalls God’s miraculous slaying of the Egyptian firstborn while “passing over” the houses of the Israelites, sparing their firstborns. The matza recalls the matzot our forefathers ate when they left Egypt for freedom. And the maror recalls the hard labor and bitter enslavement our forefathers experienced at the hands of the Egyptians.
Because the Temple is now in ruins, we are unable to offer the Paschal sacrifice; we eat the afikoman in its stead. On the Torah level, the mitzva to eat maror is contingent on eating the Paschal sacrifice; when the Pesaḥ sacrifice is not offered, there is no mitzva to eat maror. However, the Sages instituted eating maror even after the destruction of the Temple.
No change has taken place regarding the mitzva to eat matza. Thus, even after the destruction of the Temple there is a Torah commandment to eat an olive’s bulk (kezayit) of matza.
The Sages also instituted the integration into the recitation of the Hagada of four cups of wine, which we drink as an expression of joy and freedom.
They also instituted that we eat matzot and drink wine while reclining, as a demonstration of freedom.