A True Death
From the Catechism of the Catholic Church, Simplified
Mystery of the Tomb (624)
Jesus had the full experience of death, namely his soul separated from his body. This state of the dead Christ is the mystery of the tomb and his descent into hell. It is the mystery of Holy Saturday (God's Sabbath rest) after Jesus fulfilled man's salvation.
The Link Between Mortal and Immortal State (625-626)
Jesus' stay in the tomb links his passable state (before Easter) with his glorious and risen state today. "I died, and behold I am alive for evermore" (Rev 1:18). "Because Jesus allowed death to separate his soul from his body and then reunited them in the Resurrection, he is the meeting point for death and life, arresting in himself the decomposition of nature and becoming the source of the reunion for the separated soul and body" (St. Gregory of Nyssa).
During this time in the tomb, the divine person continued to possess both the human soul and the human body. "Although separated from each other, both remained with one and the same person of the Word" (St. John Damascene).
A Unique Corpse (627)
Christ's death ended his earthly human existence. However, his mortal corpse was not like others because "divine power preserved Christ's body from corruption" (St. Thomas Aquinas). His bodily Resurrection on the third day was proof because bodily decay is thought to begin on the fourth day.
Our Burial in Baptism (628)
Baptism efficaciously signifies the believer's descent into the tomb. "We were buried with him by Baptism into death." As Christ was raised from the dead so we too might "walk in newness of life" (Rom 6:4).