The Catechism sums it up nicely:
625 Christ's stay in the tomb constitutes the real link between his passible state before Easter and his glorious and risen state today. The same person of the "Living One" can say, "I died, and behold I am alive for evermore" (Rev 1:18):In other words, when Jesus commended his spirit into the hands of the Father, he simply consented to the separation of his human soul from his body. That is what death is--the separation of body and soul--and Jesus truly underwent it. But, that does not mean that his human spirit was no longer his. Jesus' human spirit is hypostatically united to his Divine Person (the Son of the Holy Trinity), so such a separation is not even possible. Therefore, when he died, his human spirit, now separated from his body but still united to his Divine Person, descended into Hades and freed the righteous souls who came before him.God [the Son] did not impede death from separating his soul from his body according to the necessary order of nature, but has reunited them to one another in the Resurrection, so that he himself might be, in his person, the meeting point for death and life, by arresting in himself the decomposition of nature produced by death and so becoming the source of reunion for the separated parts (St. Gregory of Nyssa, Orat. catech. 16).626 Since the "Author of life" who was killed (Acts 3:15) is the same "living one [who has] risen" (Lk 24:5-6), the divine person of the Son of God necessarily continued to possess his human soul and body, separated from each other by death:By the fact that at Christ's death his soul was separated from his flesh, his one person is not itself divided into two persons; for the human body and soul of Christ have existed in the same way from the beginning of his earthly existence, in the divine person of the Word; and in death, although separated from each other, both remained with one and the same person of the Word (St. John Damascene, De fide orth. 3, 27).
I hope that makes sense.