The Sacrament of Penance and Reconciliation
Those who approach the sacrament of Penance obtain pardon from God's mercy for the offense committed against him, and are, at the same time, reconciled with the Church which they have wounded by their sins and which by charity, by example, and by prayer labors for their conversion.
"Catechism of the Catholic Church 1422"
The Church has the power to forgive all sins. This forgiveness of sins is a true sacrament instituted by Christ, different from baptism, particularly on account of its judicial form. Sins are forgiven only by the sacrament of penance. Sins are forgiven by absolution which can only be given by an authorized priest. It is a real judicial pardon. The Church has the power to reserve certain cases. On the part of the sinner’s contrition, confession and satisfaction are required. Contrition is anaversion to the sins committed. Perfect contrition remits sin even before confession if it is joined with the intention to confess. Imperfect contrition (attrition) is sufficient if there is aconfession, and is a good and salutary thing. Confession must cover all mortal sins committed since baptism and not previously confessed. Venial sins, and sins already confessed can validly be confessed. And satisfaction. The effect of the sacrament is recon- ciliation with God, that is, the remission of sins and the eternal punishment but not all the temporal punishment.