Prayer is a form of communication, a way of talking to God or to the saints.
Origins of the Word
The word pray comes from the Latin word precari, which simply means to entreat or ask. In fact, although pray is not often used this way anymore, it can simply mean “please,” as in “pray continue your story.”
Talking to God
While we often think of prayer primarily as asking God for something, prayer, properly understood, is a conversation with God or with the saints. Just as we cannot hold a conversation with another person unless he can hear us, the very act of praying is an implicit recognition of the presence of God or the saints here with us. And in praying, we strengthen that recognition of the presence of God, which draws us closer to Him. That is why the Church recommends that we pray frequently and make prayer an important part of our everyday lives.
You can learn more about prayer in Prayer 101: Everything You Need to Know About Prayer in the Catholic Church.