RCIA, Rite of Christian Initiation of Adults, is for those interested in joining the Catholic church, Inquiry classes are held on Wednesday evenings. Those who wish to pursue the possibility of joining the Catholic church are assigned a sponsor who is willing to journey with the inquirer. As they enter this second phase, the people who have never been baptized in any church are considered "catechumens." Those who have been baptized are called "candidates." Together they meet on Sunday mornings to learn the fundamentals of living as a Catholic Christian.
Although the candidates may be fully initiated into the Catholic Church at any time they are considered ready by RCIA staff, they usually are fully initiated during the Easter Vigil Service along with those who also are baptized at that time.
See this article at American Catholic for more information and an extensive explanation of the various rites included in the RCIA process.
