Catechism of the Catholic Church §1447 — excerpt
Over the centuries the concrete form in which the Church has exercised this power received from the Lord has varied considerably. During the first centuries the reconciliation of Christians who had committed particularly grave sins after their Baptism (for example, idolatry, murder, or adultery) was…
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.