The Greatest Christian Feast:
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 Fulfillment of Our Faith:
Easter is a day of celebration because it represents the fulfillment of our faith as Christians. St. Paul wrote that, unless Christ rose from the dead, our faith is in vain (1 Corinthians 15:17). Through his death, Christ saved mankind from bondage to sin, and He destroyed the hold that death has on all of us; but it is His Resurrection that gives us the promise of new life, both in this world and the next.
The Coming of the Kingdom:
That new life began on Easter Sunday. In the Our Father, we pray that "Thy Kingdom come, on earth as it is in Heaven." And Christ told His disciples that some of them would not die until they saw the Kingdom of God "coming in power" (Mark 9:1). The early Christian Fathers saw Easter as the fulfillment of that promise. With the resurrection of Christ, God's Kingdom is established on earth, in the form of the Church.
New Life in Christ:
That is why people who are converting to Catholicism traditionally are baptized at the Easter Vigil service, which takes place on Holy Saturday (the day before Easter), starting sometime after sunset. They have usually undergone a long process of study and preparation known as the Rite of Christian Initiation for Adults (RCIA). Their baptism parallels Christ's own Death and Resurrection, as they die to sin and rise to new life in the Kingdom of God.
Communion - Our Easter Duty:
Because of the central importance of Easter to the Christian faith, the Catholic Church requires that all Catholics who have made their First Communion receive the Holy Eucharist sometime during the Easter season, which lasts through Pentecost, 50 days after Easter. (The Church also urges us to take part in the Sacrament of Confession before receiving this Easter communion.) This reception of the Eucharist is a visible sign of our faith and our participation in the Kingdom of God. Of course, we should receive Communion as frequently as possible; this "Easter Duty" is simply the minimum requirement set by the Church.