The Sacraments of Initiation are those events in which one comes to be one of Christ's Faithful, according to the Catechism of the Catholic Church.
There are three Sacraments of Initiation: Baptism, Confirmation, and the Eucharist. The reception of these mysteries is required for one to be considered a full member of the Catholic Church.
Children are normally baptized as infants. Adults are normally baptized after enrollment as a catechumen, either formally, as in the Latin Rite, or more informally, as in some Eastern Catholic Churches. Though not a true member of the Church, catechumens may have some share in Christ, according to the Church.
According to the Catechism, Baptism makes one a member of Christ's Body and prepares one for the reception of the other sacraments. Confirmation is the anointing in the Holy Spirit. The Eucharist gives one the "food of eternal life", and allows one to receive and conform to Jesus Christ.