The Order of Christian Initiation of Adults (OCIA) is the means by which new Catholics are formed and receive membership into the Roman Catholic Church. 

The people who are part of the OCIA are unbaptized persons, those who have never been Christian or validly baptized. 

Others who wish to enter the Catholic Church from another Christian denomination and have received a valid baptism are those who seek "full communion," and may be admitted into the Church at any time of year, provided they have been found ready to enter. They may be placed in a formation group separate from those in the OCIA.  Likewise, baptized Catholics who never received Confirmation and/or First Holy Communion and are un-catechized are placed in the same kind of group for formation to receive those sacraments. (drvc.org)