"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." (Catechism of the Catholic Church #1285)
“They [the faithful] are more perfectly bound to the Church by the sacrament of Confirmation, and the Holy Spirit endows them with special strength so that they are more strictly obliged to spread and defend the faith, both by word and by deed, as true witnesses of Christ.” (Vatican II; Dogmatic Constitution on the Church #11)
The celebration of this Sacrament is the full outpouring of the Holy Spirit on those who receive it. It makes us more aware of our relationship with the Father, unites us more closely to Christ, increases the gifts of the Holy Spirit in us, strengthens and makes more perfect our bond with the Church, and obliges us, with increased courage and without shame, to defend the faith by word and deed as true witness of Christ. Thus, it deepens and completes the grace received at Baptism.