The Sacrament of Confirmation is intimately tied to the Sacrament of Baptism. It is an essential part of the process of Christian Initiation . . . in other words, reception of the Sacrament of Confirmation is necessary to be a fully initiated member of the Church. If you stop and think about it, such a thing matches perfectly with our human nature.
Think of a newborn baby for a moment. That baby, from the moment of its conception, is a member of the human family. But when the baby is born, there are a lot of things that it simply cannot do yet. A newborn baby, in fact, can’t do most things for itself. As that baby grows and matures, however, it will become able to do more and more things, e.g. feed itself, dress itself, go places on its own, etc. These things are all a result of the process of maturation and strengthening. The fully grown person can do all sorts of things the newborn cannot, simply because the fully grown person is stronger.
The Sacrament of Confirmation corresponds to this maturation and strengthening. We receive the faith in Baptism, but we are then infants in the faith. Our faith needs to grow and get stronger if we are to be able to do what Christ commissions us to do in Baptism, namely spread the Gospel. And we know that we cannot cause our faith to grow on our own. We need God to do that for us. God, of course, knows this, and in His love for us provides us with a Sacrament by which we can see Him doing it . . . the Sacrament of Confirmation.
In the Sacrament of Confirmation, the Church uses oil, specifically Chrism blessed by the bishop. Oil is a natural strengthener. (Did you know, for example, that when someone shows cattle at the Nebraska State Fair, it’s against the rules to rub the cows down with oil, because it will make their bodies “fuller?”) So in Confirmation, the person to be confirmed is anointed with oil on the forehead. When we see that happening, we know something is being strengthened. And through the eyes of faith, we see God Strengthening that person’s faith, to be able to live it as a Christian adult and bring the Gospel to the world.