Baptism is the one sacrament that all Christian denominations share in common. In the Catholic Church, infants are baptized to welcome them into the Catholic faith and to free them from the original sin they were born with. Since the New Testament era, the Catholic Church has taught that it is a sacrament which accomplishes the remission of sin, both original sin and actual sin—only original sin in the case of infants and young children, since they are incapable of actual sin; and both original and actual sin in the case of older persons.
A person being baptized in the Catholic Church is expected to dress in white to symbolize purity of faith and the cleansing power of Baptism. The white garment symbolizes the white garments Jesus wore when he was placed in the tomb after his death on Good Friday. An infant may wear a baptismal gown handed down for generations; an adult typically puts on a full-length white gown known as an alb.
The baptism ritual is a participatory one, with all attendees rejecting Satan and professing their faith, with parents and of an infant and the godparents and immediate family members of the person being baptized being a bit more involved. Like the Sacrament of Confirmation and the Sacrament of Holy Orders, as a Catholic, you’re baptized just once. These three sacraments confer an indelible mark on your soul. No one can ever be un-baptized or re-baptized.