Baptism is a Christian sacrament marked by ritual use of water and admitting the recipient to the Christian belief.

b :a non-Christian rite using water for ritual purification, so that the person may fully complete the initiation of his conversion to Christianity. 

The word baptism originates from the Hebrew word called “Mikvah or Mikveh”.

The religion of Abraham called “Judaism” which was passed down to the Jewish nation, practiced a ritual of immersing in water called Mikvah.
Thus he who is immersed in water was purified from all uncleanness.

(To go though water, to separate one’s life from uncleanness via the act of immersing in water-the crossing of the red sea and the river of Jordan).

Baptism is an act, experience, or ordeal by which one is purified, sanctified, initiated, or named. 

In Christianity (Catholic Church), the sacrament of admission to the church, symbolized by the pouring or sprinkling of water on the head or by immersion in water 

The ceremony is usually accompanied by the words “I baptize you in the name of the Father, and of the Son, and of the Holy Spirit.” Indeed, Christians believe that after his resurrection, Jesus appeared to his disciples and commanded them to baptize in the name of the Father, Son, and Holy Spirit. In the teaching of St. Paul, it signifies the wiping away of past sins and the rebirth of the individual into a new life.