In the earliest days of the church, there was no “Protestant” or “Catholic” in the denominational sense. There was just “Church”. There were five (or 6 if the Benedictus is separated from the Sanctus) parts that took place in every church service:
First, I was made aware of my sin and cried out to God (Kyrie).
Secondly, I rejoiced mightily when salvation was granted (Gloria).
Third, I have spent my life since then studying the Word of God in order to determine just WHAT I believe (Credo).
In response to the study of the Word, we worship (Sanctus) and reflect.
As we prepare to leave, we are blessed (Benediction)
6. Agnus Dei
And we go into the world to declare the “Lamb of God Who Takes Away the Sin of the World” (Agnus Dei).
Kyrie: The penitent’s prayer
Gloria: Glory to God in the highest…
Credo: I believe in the Father…
Sanctus: Holy Holy Holy
Agnus Dei: O Lamb of God