The opening prayer is printed in the book of prayers used by the priest called the Sacramentary. When the priest says, “Let us pray,” we should all be praying our intentions to God. Then when the priest voices aloud the opening prayer, also known as the collect prayer, he is gathering or collecting all of our prayers together and offering them to God. We then respond to all of these prayers, spoken and silent, with a resounding, Amen. When we say the word, Amen, we are speaking a Hebrew word meaning, so be it.
After the opening prayer we have now gone through the introductory rites to the Mass. We need this time together in prayer to step out of the normal routine of life and into a prayerful composure to focus our hearts and minds on the rest of the liturgy.