The sacrament of penance is also called the sacrament of reconciliation, sacrament of conversion or confession. Christ instituted the sacrament immediately after his resurrection.
The sacrament of Baptism washes away or original sin and any sins committed before baptism; the Sacrament of Penance forgives sins committed after baptism. We can acknowledge our sins privately and ask for God ís mercy and forgiveness. However, when we are conscious of a serious or mortal sin, we are bound by Jesus and the Church to go to confession. (1John5:16-17)
Ask yourself: If Jesus meant that we should not go to confession to a priest, that we should only confess privately in our room; what is the relevance of the singular action of Jesus bestowing on the Apostles and His Church the power to forgive and retain sins? In truth, approached with a reverent attitude, the sacrament of penance is a sure guarantee our sins are forgiven. Through a this sacrament, we return to God like prodigal sons and daughters, and receive healing, reorientation, and true conversion.
Jesus said to them again, ” Peace be with you. As the Father has sent me, even so I send you. ‘ And when he had said this, he breathed on them, and said to them,” Receive the Holy Spirit. If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained. ” (John 20:21-23)
Therefore, if any one is in Christ, he is a new creation; the old has passed away, behold, the new has come. All this is from God, who through Christ reconciled us to himself and gave us the ministry of reconciliation; that is, in Christ, God was reconciling the world to himself, not counting their trespasses against them, and entrusting to us the message of reconciliation.
(2 Corinthians 5:17-19)
Teaching of the Church
It is called the sacrament of conversion because it makes sacramentally present Jesus” call to conversion, the first step in returning to the Father from who one has strayed by sin. It is called the sacrament of penance, since it consecrates the Chris-tian sinnerís personal and ecclesial steps of conversion, penance, and satisfaction. It is called the sacrament of confession, since the disclosure or confession of sins to a priest is an essential element of this sacrament. In a profound sense, it is all a “confession” – acknowledgement and praise – of the holiness of God and of his mercy
toward sinful man. (Catechism of the Catholic Church, 1423-1424)