In the sacrament of penance the faithful who confess their sins to a legitimate minister, are sorry for them, and intend to reform themselves obtain from God through the absolution imparted by the same minister forgiveness for the sins they have committed after baptism and, at the same, time are reconciled with the Church Which they have wounded by sinning.

Code of Canon Law

To speak of reconciliation and penance is for the men and women of our time an invitation to rediscover, translated into their own way of speaking, the very words with which our savior and teacher Jesus Christ began his preaching: "Repent, and believe in the Gospel"

St. John Paul II - Reconciliation and Penance

If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness 

1 John 1: 9