“The Lord said to Peter: “I will give you the keys of the kingdom of heaven, and whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven” (Matthew 16:19). On the day of Pentecost Peter preached the forgiveness of sins by baptism: “Repent and let every one of you be baptized in the name of Jesus Christ for the remission of sins” (Acts 2:38). Since then the Church has never failed to call people from sin to conversion and through the celebration of penance to show the victory of Christ over sin.” (The Rites: The Rite of Penance #1)
First, through the sincere expression of contrition for sin, by confessing this sin(s) to a priest, and by firmly intending to amend one’s behavior, the faithful experience spiritual healing, and receive absolution of their sin(s) from God. Secondly, through a fruitful celebration of this sacrament the faithful are reconciled to Christ and his Church.