There are different kinds of spiritual gifts but the same Spirit;
there are different forms of service but the same Lord;
there are different workings but the same God who produces all of them in everyone.
To each individual the manifestation of the Spirit is given for some benefit.
(1 Corinthians 12:4-7)

The Catechism of the Catholic Church says this of Confirmation:

In the Old Testament the prophets announced that the Spirit of the Lord would rest on the hoped-for Messiah for his saving mission. The descent of the Holy Spirit on Jesus at his baptism by John was the sign that this was he who was to come, the Messiah, the Son of God. He was conceived of the Holy Spirit; his whole life and his whole mission are carried out in total communion with the Holy Spirit whom the Father gives him “without measure.”

This fullness of the Spirit was not to remain uniquely the Messiah's but was to be communicated to the whole messianic people. On several occasions, Christ promised this outpouring of the Spirit, a promise which he fulfilled first on Easter Sunday and then more strikingly at Pentecost. Filled with the Holy Spirit the apostles began to proclaim “the mighty works of God,” and Peter declared this outpouring of the Spirit to be the sign of the messianic age. Those who believed in the apostolic preaching and were baptized received the gift of the Holy Spirit in their turn.

“From that time on the Apostles, in fulfillment of Christ's will, imparted to the newly baptized by the laying on of hands the gift of the Spirit that completes the grace of Baptism. For this reason in the Letter to the Hebrews, the doctrine concerning Baptism and the laying on of hands is listed among the first elements of Christian instruction. the imposition of hands is rightly recognized by the Catholic tradition as the origin of the sacrament of Confirmation, which in a certain way perpetuates the grace of Pentecost in the Church.”

Very early, the better to signify the gift of the Holy Spirit, an anointing with perfumed oil (chrism) was added to the laying on of hands. This anointing highlights the name “Christian,” which means “anointed” and derives from that of Christ himself whom God “anointed with the Holy Spirit.”  This rite of anointing has continued ever since, in both East and West. For this reason, the Eastern Churches call this sacrament Chrismation, anointing with chrism, or myron which means “chrism.” In the West, Confirmation suggests both the ratification of Baptism, thus completing Christian initiation, and the strengthening of baptismal grace - both fruits of the Holy Spirit.

• From this fact, Confirmation brings an increase and deepening of baptismal grace.
• From this fact, Confirmation brings an increase and deepening of baptismal grace.
• It roots us more deeply in the divine filiation which makes us cry, “Abba! Father!”
• It unites us more firmly to Christ.
• It increases the gifts of the Holy Spirit in us.
• It renders our bond with the Church more perfect.
• It gives us a special strength of the Holy Spirit to spread and defend the faith by word and action as true witnesses of Christ, to confess the name of Christ boldly, and never to be ashamed of the Cross.