Baptism unites us to God in Jesus Christ by the grace of the Holy Spirit, and incorporates us into his mystical body, the church. It cleanses us of the original sin of Adam and Eve and its eternal effects by which all their descendants (except for the Blessed Virgin Mary) are separated from God from their conception.
Baptism also takes away all personal sins and their temporal, damaging effects in us (temporal punishment). At baptism, we become children of God in oneness with Jesus Christ, God’s only-begotten son, by the grace of the Holy Spirit.