Confirmation is usually the next step after baptism, and it marks the point in the Christian journey where those who have been baptised, otherwise known as Christened, earlier in their lives make a firm commitment to Christianity. Typically older children make this decision by themselves, although people of all ages are welcomed to be confirmed! There really isn't an age limit at all when it comes to confirmation.
During the ceremony, through prayer and the laying on of hands by a bishop, the Church asks God to give those being confirmed power, through the Holy Spirit, to live a long life of faith and commitment to his Church. Unlike baptism as a baby, confirmation is an individual choice, and as such has a much greater meaning to those who choose to do it.