The process of becoming Catholic is referred to as the OCIA. It stands for Order of Christian Initiation of Adults. The words in the title, “Christian initiation” indicate that it is for adults who are not already Christians. In other words, they have never been baptized. The OCIA has also been extended to include a second group of adults: those who are already baptized but are not Catholic.
Why do people come in to the OCIA? It's different for each person. Here are reasons given by new converts:
An apprentice learns on the job by working with a person with experience. In the OCIA program, the person who is considering becoming Catholic participates in the life of the parish, guided and accompanied by a sponsor. The OCIA is a combination of fun, spiritual growth, service projects, feeling like you belong, worshiping as a member of the parish community, knowing others when you come to church, informal discussions about the Catholic faith, scriptures and the teachings of the Catholic Church. It builds on one’s own personal faith journey that each of us have been on since the day we were born.