Lent officially ends when the Triduum begins, with the celebration of Holy Thursday.
Here's a descripion of Palm Sunday through Easter Sunday.
Palm Sunday – This day is called Palm Sunday because when Jesus entered Jerusalem for the last time, the people laid palm branches on the road before Him, to honor His coming. On Palm Sunday, the Passion of Jesus is read. The vestments worn by the priests are red because we hear how Jesus shed His blood for our salvation.
The Triduum is the last three days of Holy Week. It encompasses Holy Thursday, Good Friday and Holy Saturday. Lent officially ends when the Triduum begins, with the celebration of the Lord’s Supper on Holy Thursday night.
Holy Thursday celebrates The Last Supper and The Institution of the Eucharist. During the Last Supper, Jesus washed the feet of his disciples to show that we cannot be His disciples if we are not willing to serve others. Extra bread and wine are consecrated to be used on Good Friday.
On Good Friday we celebrate Jesus’ passion – His suffering, crucifixion and death on the cross. The liturgical color on this day is red. This is the only day of the year that Mass is not celebrated. We deny ourselves the awesome gift of the Mass both to help ourselves realize what a gift the Mass is and to realize that without Jesus’ sacrificial death on the cross we would not have the Mass. We can receive Holy Communion on this day without the consecration in a Mass because consecrated hosts from the Holy Thursday celebration are reserved for this Communion service.
The Easter Vigil is the evening celebration on Holy Saturday. This celebration begins after sundown to ensure that the celebration begins in darkness. The darkness symbolizes our lives without God, without the Light of the World, Jesus Christ. During the Easter Vigil the story of salvation history is told through a sequence of nine readings. The Alleluia, which means “Praise God” is reintroduced just before the Gospel.
On Easter when Jesus rises from the dead, the liturgical color is white . Easter is actually celebrated for eight days which is why it is called the Octave of Easter. The season of Easter is celebrated for fifty days. The Ascension is celebrated near the end of Easter and it celebrates Jesus’ return to heaven and acknowledges that His physical existence on earth as a human being has ended. Easter officially comes to a close with the celebration of the Pentecost.
Source:
Catholic Faith Facts by Theresa K. Driscoll