Jesus himself was baptised in the River Jordan and he encouraged his followers to go and baptise others as well. Ever since, Christian people have understood that baptism is about a decision to become a disciple of Jesus and it marks the start of a journey of faith.
It's a journey which involves turning away from the darkness of self-centredness so that we can turn towards Jesus and live life his way. Baptism also means that we become members of the local and worldwide Christian family (i.e. the Church).
While most people are familiar with being baptised as a child, baptism can happen at any age. What matters is that those concerned believe it is right to ask for baptism. For many teenagers and adults who were not christened as children, we have been privileged to help them be baptised when they asked for it.
Baptism can only take place once in a person's life. Baptism is considered by the Church to be a 'sacrament'. In other words, it is a visible sign on the outside of something that God's love is doing on the inside of each person. In baptism, we are thanking God for his gift of life and publicly acknowledging his love. We are acknowledging that we need to turn away from selfishness and sin and make a new start with God.