Baptism is one of the seven sacraments of the Catholic Church. Jesus was baptized by John the Baptist. People get baptised to show they belong to the Christian faith. They promise that they will try to live in a Christian way. Usually it is a baby getting baptised. Obviously a baby can't make any promises, so the parents and God-parents make the promises for the baby.
When a baby is baptised it wears white. Long ago, new Christians were given a white garment to wear as a sign of their new life. White stands for purity and innocence and the rejection of sin (doing wrong things).The priest welcomes the child and the parents at the door of the church. In each Catholic Church is a great paschal candle, which stands for the resurrection of Jesus. Jesus said, "I am the light of the world", so the candle is a symbol of this.
With light we see things clearly. Jesus was talking about showing the difference between right and wrong, good and evil. In the baptism, a candle is given to one of the parents or God parents who lights it from the great paschal candle. The candle is a sign of how they hope the child will always try to live the way the Jesus would want. At the door, the priest asks the parents and God-parents if they are willing to bring up the child as a Christian. When they say 'Yes' the priest welcomes and names the child and says:
"I claim you for Christ our Saviour by the Sign of his Cross".
The priest then traces the sign of the cross on the child's forehead and the parents and God-parents do the same. The sign of the cross is a symbol that the child now belongs...