Catechism of the Catholic Church §535 — excerpt
Jesus' public life begins with his baptism by John in the Jordan. John preaches "a baptism of repentance for the forgiveness of sins". A crowd of sinners - tax collectors and soldiers, Pharisees and Sadducees, and prostitutes - come to be baptized by him.
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.