Pascha or Easter is the same thing and it is a name of a festival of Christianity. This celebration is also called Resurrection Sunday. Christian people believe that in this day Jesus Christ was killed and the day is also known as Resurrection of Jesus. People can know about the Easter from the New testament and it is not ordered from God to celebrate the day. Christian people keep fasting, pray and ask forgiveness (Penance) for 40 days. They try to keep them away from any sin and pray these days. This festival is very special to the Christian and they give special value to this Festival.
The Holy Week starts before the Easter and in the week commemorating the Maundy and Last Supper, Easter Triduum, including Maundy Thursday, as well as Good Friday, commemorating the killing and death of Jesus are contained. This festival has no any fixed date according to the English calendar. This festival celebrates in different countries in different ways. This festival is celebrated like Passover which is a festival of Jews. In USA and other countries, you will find the festival and if you want to know detail about the Easter, then you need to Visit Wikipedia.