What is confirmation in Catholic Church?

Answer 1

Roman Catholic AnswerConfirmation is the the last sacrament of initiation that we usually receive (in the Western Church) after Baptism, Penance, and Holy Communion (note: Penance is not one of the sacraments of Initiation, those are Baptism, Eucharist, and Confirmation).

from The Catechism of the Catholic Church, second edition, English translation 1994:

Confirmation is necessary for the completion of baptismal grace. (Cf. Roman Ritual, Rite of Confirmation (Ordo confirmationis), Introduction 1. 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." (Lumen Gentium 11; cf. Ordo confirmationis, Introduction 2.