This is directly from Part I of the Catechism. I posted this on another thread. Not sure if that is what from which this question stemmed (stupid English language). But follow the links to scripture, it should help.
**Paragraph 1. CHRIST DESCENDED INTO HELL
**632 The frequent New Testament affirmations that Jesus was “raised from the dead” presuppose that the crucified one sojourned in the realm of the dead prior to his resurrection.
477 This was the first meaning given in the apostolic preaching to Christ’s descent into hell: that Jesus, like all men, experienced death and in his soul joined the others in the realm of the dead. But he descended there as Saviour, proclaiming the Good News to the spirits imprisoned there.
478
633 Scripture calls the abode of the dead, to which the dead Christ went down, “hell” - Sheol in Hebrew or Hades in Greek - because those who are there are deprived of the vision of God.
479 Such is the case for all the dead, whether evil or righteous, while they await the Redeemer: which does not mean that their lot is identical, as Jesus shows through the parable of the poor man Lazarus who was received into “Abraham’s bosom”:
480 "It is precisely these holy souls, who awaited their Saviour in Abraham’s bosom, whom Christ the Lord delivered when he descended into hell."
481 Jesus did not descend into hell to deliver the damned, nor to destroy the hell of damnation, but to free the just who had gone before him.
482
634 "The gospel was preached even to the dead."
483 The descent into hell brings the Gospel message of salvation to complete fulfilment. This is the last phase of Jesus’ messianic mission, a phase which is condensed in time but vast in its real significance: the spread of Christ’s redemptive work to all men of all times and all places, for all who are saved have been made sharers in the redemption.
635 Christ went down into the depths of death so that "the dead will hear the voice of the Son of God, and those who hear will live."
484 Jesus, “the Author of life”, by dying destroyed "him who has the power of death, that is, the devil, and [delivered] all those who through fear of death were subject to lifelong bondage."
485 Henceforth the risen Christ holds “the keys of Death and Hades”, so that "at the name of Jesus every knee should bow, in heaven and on earth and under the earth."
486