Article 5: He descended into hell.The third day he arose again from the dead.

"Hell" here means the abode of the dead which is sheol in Hebrew and hades in Greek (cf. Acts 2:31).

From Pope John Paul II's catechesis January 11, 1989: The formula is derived from numerous New Testament texts. The first is found in the Apostle Peter's discourse on Pentecost. Referring to Psalm 16 to confirm the announcement of Christ's resurrection which it contains, Peter stated that the prophet David "foresaw and spoke of the resurrection of the Christ, that he was not abandoned to Hades, nor did his flesh see corruption" (Acts 2:31). The Apostle Paul's question in the Letter to the Romans has a similar meaning: "'Who will descend into the abyss?' (that is, to bring Christ up from the dead)" (Rom 10:7). Also in the Letter to the Ephesians there is a text which asks a significant question in reference to a verse of Psalm 68: "When he ascended on high he led a host of captives, and he gave gifts to men" (Ps 68:19). "In saying, 'he ascended,' what does it mean but that he had also descended into the lower parts of the earth? He who descended is he who also ascended far above all the heavens, so that he might fill all things" (Eph 4:8-10). In this way Paul seems to link Christ's "descent" into the abyss (among the dead, of which he speaks in the Letter to the Romans), with his ascension to the Father, which begins the eschatological "fulfillment" of all things in God. A reading from an ancient homily for Holy Saturday:

"What is happening? Today there is a great silence over the earth, a great silence, and stillness, a great silence because the King sleeps; the earth was in terror and was still, because God slept in the flesh and raised up those who were sleeping from the ages. Read More.. From Pope Benedict XVI General Audience November 5, 2008 "If Christ has not been raised, then our preaching is in vain and your faith is in vain... and you are still in your sins" (1 Cor 15: 14-17). With these strong words from the First Letter to the Corinthians, St Paul makes clear the decisive importance he attributes to the Resurrection of Jesus. In this event, in fact, lies the solution to the problem posed by the drama of the Cross.

The Cross alone could not explain the Christian faith, indeed it would remain a tragedy, an indication of the absurdity of being. [studenica_fresco] ​

The Paschal Mystery consists in the fact that the Crucified man "was raised on the third day, in accordance with the Scriptures" (1 Cor 15: 4), as proto-Christian tradition attests. This is the keystone of Pauline Christology: everything rotates around this gravitational centre. The whole teaching of Paul the Apostle starts from, and arrives at, the mystery of him whom the Father raised from the dead. Read more about St. Paul's teachind on the Cross and Resurrection...

Dux vitae, mortuus, regnat vivus! The Lord of life was dead; but now he is alive and triumphs (Easter Sequence)

From the Catechism of the Catholic Church:

654 The Paschal mystery has two aspects: by his death, Christ liberates us from sin; by his Resurrection, he opens for us the way to a new life. This new life is above all justification that reinstates us in God's grace, "so that as Christ was raised from the dead by the glory of the Father, we too might walk in newness of life." Justification consists in both victory over the death caused by sin and a new participation in grace.⁵²⁶ It brings about filial adoption so that men become Christ's brethren, as Jesus himself called his disciples after his Resurrection: "Go and tell my brethren."⁵²⁷ We are brethren not by nature, but by the gift of grace, because that adoptive filiation gains us a real share in the life of the only Son, which was fully revealed in his Resurrection.