Now for the long answer:
Jesus came into the world to save sinners [1 TIM 1:15] through his death on the cross.
Jesus, while he was on earth, instituted the Church and the Priesthood. He also instituted the sacrament of CONFESSION in which he gave his authority to forgive sins to his disciples. This is recorded in Sacred Scripture [John 20:19-23]:

19 On the evening of that day, the first day of the week, the doors being shut where the disciples were, for fear of the Jews, Jesus came and stood among them and said to them, "Peace be with you." 20 When he had said this, he showed them his hands and his side. Then the disciples were glad when they saw the Lord. 21 Jesus said to them again, "Peace be with you. As the Father has sent me, even so I send you." 22 And when he had said this, he breathed on them, and said to them, "Receive the Holy Spirit. 23 If you forgive the sins of any, they are forgiven; if you retain the sins of any, they are retained."

The catechism of the Catholic Church (CCC) states in paragraph 1442:

1442 Christ has willed that in her prayer and life and action his whole Church should be the sign and instrument of the forgiveness and reconciliation that he acquired for us at the price of his blood. But he entrusted the exercise of the power of absolution to the apostolic ministry which he charged with the "ministry of reconciliation. [2 COR 5:18] The apostle is sent out "on behalf of Christ" with "God making his appeal" through him and pleading: "Be reconciled to God. [2 COR 5:20]