In the sacrament of Confirmation, the grace bestowed at Baptism is strengthened and given a kind of seal.  In the Roman rite of the Church, this sacrament is ordinarily administered by the bishop before or during early adolescence.  

This practice emphasizes the “strength and full growth in the Spirit” communicated by this sacrament, as well as communion in the Church, expressed in particular by the presence and activity of the bishop.  In Eastern-rite churches, this sacrament is conferred at the same time as Baptism, thereby emphasizing the close unity of these two sacred signs, as well as their connection to the Eucharist, which is also received by the child who is thus fully initiated into the sacramental mysteries.

{excerpt  taken from Ascencion Press "Journey thru the Catechism"}