Response:
I am not sure just when the use of holy, or blessed, water began, but it goes way back in history. It is ordinary water that has been blessed. I think it's most common use is to remind us of our Baptism, and that our Baptism was our entrance into the Christian life and the salvation that comes from the death and Resurrection of Jesus. We have holy water at the doors of our churches, usually, so that the water and the sign of the cross will remind us of who we are and where we are, refreshing us in our Baptismal life. And sometimes the Opening Rite of the Eucharist is a sprinkling, for the same sort of reason -- Baptism has made us the People who are united in the Body and Blood of Christ.

The water is also sprinkled on people and objects that relate to our living the Christian life, like our churches, our homes. our crucifixes and rosaries and medals, a couple getting married, and so on as part of the Church's blessing of all these people and events and things. Everything we do as Christians comes from our Baptism, and the water serves as a sign that all of our lives, our words, our actions, our choices, our commitments, the objects we use, are drawn together into a wonderful unity by the effects of our Baptism, and so we do what Paul asked of us: "Whatever you do, do all for the glory of God."

The whole Church hopes that we will grow deeper in our desire to live the Christian life as fully and as completely as our Baptism asks of us. The water reminds us that we are saved by Jesus, and are the People of God, the Body of Christ, the Church.