Easter is the greatest feast in the Christian calendar. On this Sunday, Christians celebrate the resurrection of Jesus Christ from the dead. For Catholics, Easter Sunday comes at the end of 40 days of prayer, fasting, and almsgiving known as Lent. Through spiritual struggle and self-denial, we have prepared ourselves to die spiritually with Christ on Good Friday, the day of His Crucifixion, so that we can rise again with Him in new life on Easter.
The first name comes from the fact that it commemorates Jesus' triumphal entry into Jerusalem, when the crowd had palm branches (John 12:13). The second name comes from the fact that the narrative of the Passion is read on this Sunday.