The Baptism of adults
Since the beginning of the Church, adult Baptism is the common practice where the proclamation of the Gospel is still new. The catechumenate (preparation for Baptism) therefore occupies an important place. This initiation into Christian faith and life should dispose the catechumen to receive the gift of God in Baptism, Confirmation, and the Eucharist.
Source: Catechism of the Catholic Church (Vatican.va)