Confirmation is one of the seven sacraments of the Catholic Church. It is the one of the three sacraments of initiation into the Catholic Church, the other two being Baptism and First Holy Communion.
According to Catholic doctrine, in the sacrament of Confirmation, the faithful are sealed with the gift of the Holy Spirit and are strengthened in their Christian life.
The Catechism of the Catholic Church states:
Recall then that you have received the spiritual seal, the Spirit of wisdom and understanding and courage, the spirit of right judgment and courage, the spirit of knowledge and reverence, the Spirit of holy fear in God's presence. Guard what you have received. God our Father has marked you with his sign; Christ the Lord has confirmed you and has placed his pledge, the Spirit, in your heart.
The Catechism of the Catholic Church sees as a scriptural basis for Confirmation as a sacrament distinct from Baptism the account in the Acts of the Apostles 8:14-17:
Now when the apostles, who were in Jerusalem, had heard that Samaria had received the word of God, they sent unto them Peter and John. Who, when they were come down, prayed for them, that they might receive the Holy Ghost. For he was not as yet come upon any of them; but they were only baptized in the name of the Lord Jesus. Then they laid their hands upon them, and they received the Holy Ghost.
In the Latin Church (i.e. Western Catholic Church), the sacrament is to be conferred on the faithful at about the age of discretion (generally taken to be about 7), unless the Episcopal Conference has decided on a different age, or there is danger of death or, in the judgment of the minister, a grave reason suggests otherwise. Even in those countries where the episcopal conference has set a later age as normal, a bishop may not refuse to confer the sacrament on younger children who request it, provided they are baptized, have the use of reason, are suitably instructed and are properly disposed and able to renew the baptismal promises (letter of the Congregation for Divine Worship and the Discipline of the Sacraments published in its 1999 bulletin, pages 537–540).