Holy Baptism is the basis of the whole Christian life, the gateway to life in the Spirit, and the door which gives access to the other sacraments. Through Baptism we are freed from sin and are reborn as sons of God; we become members of Christ, are incorporated into the Church, and made sharers in her mission: "Baptism is the sacrament of regeneration through water in the word."
Catechism of the Catholic Church (1213)
Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and the Son, and of the Holy Spirit, teaching them of observe all that I have commanded of you.
Are you unaware that you died?
The Fruit of Baptism, or Baptismal grace, is a rich reality that includes forgiveness of original sin and all personal sins, birth into the new life by which man becomes an adoptive child of the Father, a member of Christ, and a temple of the Holy Spirit. By this very fact the person baptized is incorporated into the Church, the Body of Christ, and made a sharer in the priesthood of Christ.
Catechism of the Catholic Church (1279)