Baptism or Christening (same thing), is a symbolic ceremony using water to show the washing away of sin. 'But my baby is perfect, and she's never done anything wrong', I hear you say, and that is why baptism is only done once, as it covers the person all of their life. For things we do wrong in our future, only known to God. These things will also be washed away (forgiven), when we turn away from doing those wrong things and ask for forgiveness then don't do or say those things again.

God will forgive us every time we ask, but we take ourselves further from the heaven on earth each time we sin. So each time we ask for forgiveness, God does so and that heals the relationship between us...that is what being righteous is - being in a right (good) relationship with God.

Young children have these promises made for them on behalf of their parent/s or guardians. As such a Child's baptism is a start to a relationship with God, through knowing Jesus in the power of Holy Spirit (God within us). 

This relationship with God is grown in the nurturing environment of the Church. A place to learn about what God says to us in the bible. Within this loving relationship with God, there also grows loving relationships between the people. This is why people are baptized into a Church, so they can share and be surrounded by the living embodyment of God on earth - Christians.

To be set free from things we do wrong, we need Gods grace to forgive us because God is not compelled to do anything other than his will (what God wants). This graceful forgiveness was made possible by God himself. Jesus (who was and is innocent) was killed by people's actions, but Jesus came back to life, which is what God wants for all of us - to have new life, set free from what we do wrong (sin).