The Gloria (Latin for "glory") is a beautiful prayer that we sing towards the beginning of Mass, meant as a way to direct our praises to God in celebration of His coming as a man 2000 years ago.

Confident that the Lord will forgive us our sins, we now sing out, giving praise to God in imitation of the angels in heaven. This prayer of the Mass is actually an ancient hymn with three parts. The first part is the song that the shepherds heard sung by the heavenly choir of angels at the birth of Christ: "And suddenly there was a multitude of the heavenly host with the angel, praising God and saying, 'Glory to God in the highest and on earth peace to those on whom his favor rests.'" Luke 2:13–14. The second part praises God by recalling all his attributes. The third part prays to Jesus, asking Him to save us from our sins.

After calling to mind our sinfulness both in the Confiteor and Kyrie, we now call to mind the Incarnation of God. This is a prayer to God the Father, reminding Him that the Church gathered in this building is the incarnate Body of His Son. To do this, we sing a Christian song… the song the angels sang to the shepherds in Bethlehem.

Monsignor Ronald Knox, in a book called The Mass in Slow Motion, written in 1949, spoke of the Gloria as a time to cheer us up after groveling in the first part of the Mass. In case we get too down on ourselves, this prayer is a means to take the focus away from us and turn it again towards God, giving God praise for sending His Son to save us from our sinful plight.

Article by Mike Dubruiel (The How-To Book of The Mass)