Seder is a very popular religious feast which is taken during the Passover Holiday. In some houses this is celebrated on the first night of the holiday whereas in the others it is celebrated both on the first and the second nights. Jewish people celebrate the event when Israelites fled out of Egypt by celebrating the Passover. They eat the festive dinner in the form of Seder along with family and friends in order to celebrate the event.
The Jewish were kept enslaved in Egypt from where they successfully escaped thus marking the end of that struggle and this is when the foundation of Passover was laid some 3000 years ago. In order to celebrate their identity and freedom, The Seder is celebrated. So that they can offer thanks and praise for a life that is free of any oppression and slavery. It is also a tradition to invite the poor and the needy along with family friends and guests to celebrate this festival. This to the Jewish people is very serious business and taken extremely seriously by them as it means the reaffirmation of their faith in many forms.
While they celebrate the Seder they have to be careful about the themes of the Seder. There are two major themes that are followed, freedom and slavery. For example when they eat the Matzo, they depict the poverty that was faced by the slaves in Egypt, faced, as Matzo was bread specifically eaten by the poor. There is another thing called Charoset which is a sweet paste, and represents the mortar the slaves used to work with. They eat bitter herbs to remind themselves of the bitterness of slavery. Wine is drunk to celebrate freedom and vegetables dipped in salt water are eaten to represent royalty and the tears of the Jewish people who were enslaved.
Although the Passover Seder is usually celebrated in the same manner everywhere yet there are a few minor differences in culture to culture. These differences have nothing to do with the concept of Seder but the way it is celebrated. In Israel it is celebrated only on the first night of the Passover whereas everywhere else it is celebrated on the second night as well. Christians lately have started taking much interest in the tradition of Seder. Though they celebrate it very much in the same manner as the Jewish, they just add a Christian prayer in the end.