Jesus calls to conversion. This call is an essential part of the proclamation of the kingdom: "The time is fulfilled, and the kingdom of God is at hand; repent, and believe in the gospel." In the Church's preaching this call is addressed first to those who do not yet know Christ and his Gospel. Also, Baptism is the principal place for the first and fundamental conversion. It is by faith in the Gospel and by Baptism that one renounces evil and gains salvation, that is, the forgiveness of all sins and the gift of new life.
Source: Catechism of the Catholic Church (Vatican.va)