Good Friday is the Friday on which the Church keeps the anniversary of the Crucifixion of Jesus Christ. St. Irenaeus and Tertullian speak of Good Friday as the day of the Pasch. From the earliest times the Christians kept every Friday as a feast day; and the obvious reasons for those usages explain why Easter is the Sunday par excellence, and why the Friday which marks the anniversary of Christ's death came to be called the Great or the Holy or the Good Friday.
The dramatic unveiling and adoration of the Cross, which was introduced into the Latin Liturgy in the seventh or eighth century, had its origin in the Church of Jerusalem, towards the close of the fourth century. A veiled image of the Crucifix is gradually exposed to view, while the celebrant, accompanied by his assistants, sings three times the Ecce lignum Crucis (Behold the wood of the Cross on which hung the salvation of the world), to which the choir answers, each time, Venite adoremus (Come let us adore).
During the singing of this response the whole assembly (except the celebrant) kneel in adoration. When the Cross is completely unveiled the celebrant carries it to the foot of the altar, and places it in a cushion prepared for it. The act in question is not intended as an expression of absolute supreme worship (latreia) but reverence (proskynesis). While we bend down in body before the cross we bend down in spirit before God. While we reverence the cross as the instrument of our redemption, we pray to Him who redeemed us.