The Rite of Christian Initiation of Adults (RCIA) is the process through which people enter the Catholic Church. This includes people who have not been baptized (called catechumens) and people who have been baptized in another Christian church and now seek full Communion with the Catholic Church.
The RCIA unfolds in a series of stages. In the first stage, a person shows initial interest in the Catholic Church and a desire to learn more. He or she is an “Inquirer.” During the next period, called the Catechumenate, the person explores the teachings of the faith in a more systematic way. At Sunday Mass the catechumens and their teachers are often dismissed after the homily for further reflection on the readings of the day.
During Lent the catechumens, now called the Elect, prepare themselves for the reception of the Sacraments of Initiation at the Easter Vigil. Those who are not baptized will receive the sacraments of Baptism, Confirmation and Eucharist. For a baptized person, reception into the Catholic Church involves reception of the Sacrament of Penance, followed by a Profession of Faith and the sacraments of Confirmation and Eucharist.
The RCIA is essentially a time of conversion, as the catechumens learn how to follow Christ more closely as a member of the Catholic community. It can also be a time of conversion for the community, which is strengthened by the catechumens’ example.
The U.S. Catholic Catechism for Adults, pp. 188-192.