In the Catholic Church, why is it important for an individual to be confirmed?

To see the importance of confirmation in the Catholic
Church, remember that Catholics are baptized as infants, not as adults the way many
Protestant sects do things.  Because of this, confirmation is an important way for the
teen (now an adult in many ways) to reaffirm the promises that were made on his or her
behalf at baptism.

At a Catholic baptism, the parents and
godparents of the child make various promises on the child's behalf.  They promise, for
example, to reject Satan and all his works.  The child cannot, of course, participate. 
When a child is 6 or 7 and takes Holy Communion, they are participating more fully in
the Church but are still really not old enough to fully understand their commitment to
the Church.

By the time that a person is confirmed, they
are old enough to really make a commitment for themselves.  This is the importance of
confirmation -- to commit yourself to God and the Church in a way that was not possible
at the time you were baptized.