The Lord himself affirms that Baptism was necessary for salvation (C.C.C. 1257).                "No one can enter the Kingdom of God without being born of water and Spirit" (John 3:5). Jesus commissioned the Apostles to preach the Gospel to all nations and baptize, telling them, "Whoever believes and is baptized will be saved" (Mark 16:16). 
Baptism erases original sin (the sin imparted to all mankind by the Fall of Adam and Eve in the Garden of Eden) and personal sins (sins committed by the person prior to receiving the Sacrament if adults).
Through Baptism we are freed from sin and reborn as sons of God. Holy Baptism is the basis of our whole Christian life, the gateway to life in the spirit, the door which gives us access to the other sacraments. Baptism is a sacrament of regeneration through water in the word.

The rite of Baptism consists in immersing the candidate in water, or pouring water on the head, while pronouncing the invocation of the Most Holy Trinity: the Father, the Son, and the Holy Spirit.”Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you” (Mt 28:19-20).