Baptism is a step of obedience in going public with your faith in Jesus, communicating to the world your decision to following Him. 

It's the next step after salvation.

Christian baptism is the immersion of a believer in water in the name of the Father, the Son, and the Holy Spirit. It is an act of obedience symbolizing the believer's faith in a crucified, buried, and risen Saviour, the believer's death to sin, the burial of the old life, and the resurrection to walk in newness of life in Christ Jesus. It is a testimony to his/her faith in the final resurrection of the dead.