The Latin word triduum refers to a period of three days and has long been used to describe various three-day observances that prepared for a feast day through liturgy, prayer, and fasting. But it is most often used to describe the three days prior to the great feast of Easter: Holy Thursday, Good Friday, and Holy Saturday and the Easter Vigil. The General Norms for the Liturgical Year state that the Easter Triduum begins with the evening Mass of the Lord's Supper on Holy Thursday, "reaches its high point in the Easter Vigil, and closes with evening prayer on Easter Sunday" (par 19).

Just as Sunday is the high point of the week, Easter is the high point of the year. The meaning of the great feast is revealed and anticipated throughout the Triduum, which brings the people of God into contact — through liturgy, symbol, and sacrament — with the central events of the life of Christ: the Last Supper, His trial and crucifixion, His time in the tomb, and His Resurrection from the dead. In this way, "the mystery of the Resurrection, in which Christ crushed death, permeates with its powerful energy our old time, until all is subjected to him" (CCC 1169). During these three days of contemplation and anticipation the liturgies emphasize the sacrificial death of Christ on the Cross, and the sacraments of baptism and the Eucharist, by which the faithful enter into the life-giving Passion of Christ and grow in hope of eternal life in Him.