Catechism Part 1, Section 2, Chapter 2, Articles 5-6: He descended into hell. On the third day he rose again. He ascended into heaven and is seated at the right hand of the Father (631-667)

Article 5: He descended into hell. On the third day he rose again. (631-658)
This article asserts both Jesus' descent and resurrection, saying that Jesus brought forth life from the depths of death.

Paragraph 1: Christ descended into hell. (632-637)
To believe in Jesus' descent into hell is to believe that Christ died like all humans die, and his soul descended into the realm of the dead to free the Spirits of  the just who had gone before him by preaching the good news. Christ went down in order for the dead to hear his voice and those who hear will live. Thus, Christ destroyed the power of death (the devil, the author of death), and delivered those who through fear of death were subject to lifelong bondage. The risen Christ hold the keys of death and Hell so that at the name of Jesus every knee shall bow , in heaven and on earth and under the earth.

Paragraph 2: On the third day He rose from the dead. (638-658)
The resurrection is a central truth to the faith. It was a real, historical event, the first sign being the empty tomb, followed by appearances to the Apostles and Mary Magdelene , who became Christ's prime witnesses and later the foundations of the Church. Given their tests of faith, it is impossible to deny the validity of their claims. Christ's resurrected body was a real, physical body, but not bound by space and time. It was not a mere return to earthly life. No one has witnessed the actual event, so it remains a transcendent mystery.
Through the resurrection, the Father raised the Son and incorporated the Son's humanity into the Trinity. Likewise, the Spirit gave life to the Son, and the Son raised himself by his divine power. The Resurrection was a reuniting of soul and body that death had separated.
The Resurrection confirms Christ's claims to divinity, and fulfills the prophecies of the Scripture. As Christ's death liberates us from sin, so the resurrection gives us hope for a new life. We are adopted by the Father through God's grace, and become brethren of Christ. Finally, the risen Christ is the source of our own future resurrection.

Article 6: He ascended into heaven and is seated at the right hand of the Father (659-664)

While Christ's resurrected body was veiled in human appearance, through the ascension he returned to divine glory, showing himself only to Paul as a human. Through the ascension, Christ opens access to the Father. Now in heaven, he acts as an intercessor on our behalf. By "sitting at the Father's right hand," we mean the glory and honor of divinity, and the beginning of the Kingdom that will have no end.