Sacrament of Confirmation

Confirmation is one of the Seven Sacraments of the Church.

Confirmation is the sacrament by which the baptized more fully join the Catholic Church. Per the Catechism (1285),

the reception of the sacrament of Confirmation is necessary for the completion of baptismal grace

Confirmation completes the grace of Baptism by a special outpouring of the gifts of the Holy Spirit, which seal of "confirm" the baptized in union with Christ and equip them for active participation in the worship and apostolic life of the Church.

The CCC reviews the sacrament of Confirmation in paragraphs 1285-1321, starting page 325

Sacrament of Confirmation overview

Per CCC 1210:

Christ instituted the sacraments of the new law. There are seven: Baptism, Confirmation (or Chrismation), the Eucharist, Penance, the Anointing of the Sick, Holy Orders and Matrimony. The seven sacraments touch all the stages and all the important moments of Christian life:1 they give birth and increase, healing and mission to the Christian's life of faith. There is thus a certain resemblance between the stages of natural life and the stages of the spiritual life.

Confirmation one of the three sacraments of "Christian Initiation":

Baptism
Confirmation
Eucharist

From CCC 1285

Baptism, the Eucharist, and the sacrament of Confirmation together constitute the "sacraments of Christian initiation," whose unity must be safeguarded. It must be explained to the faithful that the reception of the sacrament of Confirmation is necessary for the completion of baptismal grace. For "by the sacrament of Confirmation, [the baptized] are more perfectly bound to the Church and are enriched with a special strength of the Holy Spirit. Hence they are, as true witnesses of Christ, more strictly obliged to spread and defend the faith by word and deed."

"Confirmation" etymology

from:

con (with) + firmare (strengthen, make strong)
firmare from PIE *dher- "to hold firmly, support"

Scriptural Sources of Confirmation

Acts 2:1-13: , which marks what the Church celebrates as "Pentecost"

When the time for Pentecost was fulfilled, they were all in one place together. And suddenly there came from the sky a noise like a strong driving wind,* and it filled the entire house in which they were. Then there appeared to them tongues as of fire,* which parted and came to rest on each one of them. And they were all filled with the holy Spirit and began to speak in different tongues,* as the Spirit enabled them to proclaim.
....
both Jews and converts to Judaism, Cretans and Arabs, yet we hear them speaking in our own tongues of the mighty acts of God.” They were all astounded and bewildered, and said to one another, “What does this mean?”

Pentecost

John 20:19-23

Rite of Christian Initiation

Catholics or new Catholics, enter the Sacrament of Confirmation through the "rites" of confirmation