Catechism of the Catholic Church §1423 — excerpt
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 whom one has strayed by sin.
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.