Here are only three of the 55 entries about the Sacrament of Penance in the Catechism of the Catholic Church
1480 Like all the sacraments, Penance is a liturgical action. The elements of the celebration are ordinarily these: a greeting and blessing from the priest, reading the word of God to illuminate the conscience and elicit contrition, and an exhortation to repentance; the confession, which acknowledges sins and makes them known to the priest; the imposition and acceptance of a penance; the priest's absolution; a prayer of thanksgiving and praise and dismissal with the blessing of the priest.
1446 Christ instituted the sacrament of Penance for all sinful members of his Church: above all for those who, since Baptism, have fallen into grave sin, and have thus lost their baptismal grace and wounded ecclesial communion. It is to them that the sacrament of Penance offers a new possibility to convert and to recover the grace of justification. The Fathers of the Church present this sacrament as "the second plank [of salvation] after the shipwreck which is the loss of grace."
1491 The sacrament of Penance is a whole consisting in three actions of the penitent and the priest's absolution. The penitent's acts are repentance, confession or disclosure of sins to the priest, and the intention to make reparation and do works of reparation.