Easter is the oldest and most important festival of the Western Christian year, celebrating Jesus Christ's resurrection (rising from the grave) following his crucifixion on Good Friday. Easter Sunday is the culmination of Holy Week (but not part of it), and the first day of Eastertide. Easter marks the end of the 40 days of Lent. Easter Sunday (or simply Easter Day) is the first day of the Easter Week which ends on Easter Saturday.
Christ's resurrection forms the basis of Christian faith as it demonstrates Jesus to be the Son of God, and symbolizes his conquest of death.