"Gloria in excelsis Deo" is a Christian hymn known also as the Greater Doxology and the Angelic Hymn/Hymn of the Angels. The name is often abbreviated to Gloria in Excelsis or simply Gloria.
Angel with the words "Gloria in Excelsis Deo et in terra pax" by Dalziel Brothers
A doxology is a short hymn of praises to God in various forms of Christian worship, often added to the end of canticles, psalms, and hymns. The tradition derives from a similar practice in the Jewish synagogue, where some version of the Kaddish serves to terminate each section of the service.
The Eucharistic Doxology in a stained glass window of St. James' in Glenbeigh