For adults, the Church after Vatican II has restored the ancient order of the Catechumenate in the Rite of Christian Initiation of Adults (RCIA). As the American bishops explain (usccb.org), the RCIA walks adults through the steps of formation as catechumens, “bringing their conversion to the faith to a greater maturity. It helps them respond more deeply to God’s gracious initiative in their lives and prepares them for union with the Church community. This process is meant to form them into the fullness of the Christian life and to become disciples of Jesus, their teacher. This includes an initiation into the mystery of salvation, the practice of faith, hope, and love, and other virtues in a succession of liturgical rites.” Most often this initiation will lead to the catechumen’s reception at the Easter Vigil of all three Sacraments of Initiation: Baptism, Eucharist and Confirmation.
Persons already baptized into another Christian church who are now seeking full communion with the Catholic Church are also welcome to participate along with catechumens (i.e., those not yet baptized) in this process of learning about the Catholic faith and being formed in that faith. They bring to the process of preparation their prior experience of Christian life and prayer. For a baptized Christian, reception into full communion with the Catholic Church involves reception of the Sacrament of Penance and Reconciliation and then a Profession of Faith followed by the celebration of Confirmation and the Eucharist.