The 'Sacrament of Reconciliation' was traditionally known as the sacrament of penance, or confession. It was renamed "sacrament of reconciliation" by the Second Vatican Council in order to emphasize its healing effects, it's bringing the repentant person back into the graces of God.
"Who can forgive sins but God alone?" demanded the scribes and Pharisees when Jesus absolved the paralytic (Luke 5:21), and this same objection is often repeated today. When a priest absolves one from sin, it is not to say that God has contracted out part of his work to subordinates. It is still true and absolutely without exception that absolution from sin can come from God alone; for the very essence of sin lies in the fact that it is not merely a transgression of a human standard but an affront to the Sovereign Lord of the universe. If a priest were fooled or cajoled or bribed into granting absolution to someone not sincerely repentant, then the latter would not be forgiven by God, because God and God alone knows the heart. But the power of absolution means that the priest's words of forgiveness are the instrument and channel of God's forgiving grace to all who receive the sacrament worthily. The priest speaks in the name of Christ, for when Christ appeared to His disciples, after the resurrection, he told them, "Receive the Holy Spirit. Whose sins you forgive are forgiven them, and whose sins you retain are retained" (John 20:22-23).
Certainly we can always turn to God the moment we are conscious of sin, and ask forgiveness. Indeed we should do so; and if our dispositions are what they should be, He grants pardon at once. but it is not that easy to repent sincerely, especially of those sins for which we have a special weakness. It is very easy to mutter, "God, I'm sorry," without really changing our attitude. Although confession is not a sure guarantee of sincerity, the fact of having to admit our sins to another human being, and to submit our contrition to his authoritative judgment, helps considerably to keep us honest.
Likewise, it is often difficult to believe in God's pardon, especially for sins of which we are profoundly ashamed. Our timid hearts receive a powerful reassurance when one authorized to speak for Christ declares, "God the Father of mercies, through the death and resurrection of His Son, has reconciled the world to Himself. He has sent the Holy Spirit among us for the forgiveness of our sins. through the ministries of the Church, I absolve you of your sins, in the name of the Father, and of the Son, and of the Holy Spirit."
We come to the Sacrament of Reconciliation, acknowledging our guilt. We confess our sins in confidence and receive forgiveness and reconciliation, but we come to the priest as the representative of the Christian community to acknowledge that our sins have upset our relationship of love to the other members of the community. Therefore, in being forgiven, not only are we reconciled back to God, but also reconciled back into the community.