Reconciliation

Why do we have to confess our sins to a priest?
During His public ministry, Jesus forgave the sins of many people. (see Matthew 9:1-8; Luke 7:36-50; John 8:1-11). It was such a prominent part of His ministry that it can rightly be said that He either had this ability or he was a liar. During His public ministry Jesus gave his apostles the authority to cast out demons and to forgive sins. In John 20:21-23 the risen Lord Jesus appeared in the locked upper room and told them: “As the Father sent Me, so I am sending you. Receive the Holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained.” This power to pardon did not cease with the Apostles, because they consecrated bishops to continue the work of the Church until the end of time. This handing on of the authority given to the first apostles to each generation is called apostolic succession.
It is difficult to imagine how the disciples were to determine which sins were to be forgiven and which were to be retained unless the person seeking forgiveness confessed his sins to the one charged with the power to forgive in the name of God. This understanding not only has Biblical roots, but can also be traced to some of the very earliest documents written by Church fathers during the apostolic period.
When a person confesses his sins to a priest and receives absolution, through the promise of Matthew 18:15-18, the repentant sinner encounters Christ Himself.

Can a priest reveal the sins he hears in Confession?
No. Due to what is called the seal of confession the priest cannot ever tell others about the sins he hears in the confessional or even imply through his speech any connection between a person and any sins they confess. Throughout the history of the Church many priests have endured prison or worse at the hands of civil authorities who tried to get them to reveal what they heard in confession because they refused. In fact, Church law requires this of priest and the penalty for revealing someone’s sins heard in confession is the permanent loss of faculties (they can no longer validly perform any sacraments).
“Given the delicacy and greatness of this ministry and the respect due to people every confessor, without any exception and under very severe penalties, is bound to maintain ‘the sacramental seal’ which means absolute secrecy about the sins revealed to him in confession.” (Compendium of the Catechism, 309)

What are the effects of this sacrament?
“The effects of the sacrament of Penance are: reconciliation with God and therefore the forgiveness of sins; reconciliation with the Church; recovery, if it has been lost, of the state of grace; remission of the eternal punishment merited by mortal sins, and remission, at least in part, of the temporal punishment which is the consequence of sin; peace, serenity of conscience and spiritual consolation; and an increase of spiritual strength for the struggle of Christian living.” (Compendium of the Catechism, 310)