The teachings of the Catholic Church on the sacrament of baptism might be summarized in the following points:
Baptism is God’s life abiding in us. It is more than an event -- it is a transformative reality. To understand what this means, we might compare it to marriage.
We talk about marriage in two ways. Marriage is what takes place on THE DAY -- the exchange of vows, the celebration, the kiss. But marriage is what takes place every day after that. Marriage is what the marriage ceremony is for. Marriage is a ritual that expresses and initiates a new way of life. Baptism is exactly like this. Baptism is the ritual washing of a person responding in faith to the Gospel in the name of the God we worship as Father, Son, and Holy Spirit. But baptism is the new life that flows from God’s compassionate gift of Jesus to the world. You were baptized on that day, but your baptism continues to operate in you, through you -- because your baptism is the Holy Spirit living out God’s life in you.
Baptism is the public and visible sign of the beginning of our Christian journey. As we tell the story of God saving us, this story takes an immense leap forward when we come to the event of our baptism. Before baptism, our story is about what it's like to get by on our own. Even if we were baptized as infants, our story begins with a baby who has the assurance of her parents, maybe her community, but no ultimate assurance that the universe is a friendly place. But in baptism, God reaches out and assures us, "Yes, you are mine. I've got you. You will fall. You will fail. You will break. But I will pick you up, I will make up for your failures, I will heal you completely. You will never be alone, because I am delighted with you." We can count on this promise, because Jesus counted on it, and God raised Jesus from the dead.