Chord progressions are like the skeleton of the music. They are the foundation of the different songs.
For example, like T- Block wrote, the scale degrees of the C scale, you would use those scale degrees to figure
out the skeletal structure of the music. They give you a clue of what will come next. This is the purpose of progressions in gospel music. It kind of comes from the Classical music structure, but they use different progressions in their music.
Roman numerals were also a convention of the classical system that is used to describe the different functions of the chords used for the songs. Again, this was converted to gospel music to easily be able to tell what was going on in different places of the music.
It is not enough to know that you are play a C chord, but what context you are playing that C chord in. for example, in the key of C major, a C chord is a 1 chord, and therefore major, and the tonic(the place where the music is at "home") in the key of G major, a C chord is a 4 chord, and therefore also major, but used different than a C chord in the key of C, because it is not at home. In Bb major, the C chord is a 2 chord, and is therefore minor, and is certainly not the same as the keys C and G.
As an example of chord progressions, on the C scale let me list it here for you:
C-1 D-2 E-3 F-4 G-5 A-6 B-7 C-8 these numbers represent scale degrees(T-block also posted about a progression in another post)
The most basic progression that is always used is a 2-5-1. This is whether you are playing, classical, jazz or gospel. The difference is the way they are played. You probably already play a 2-5-1 without knowing it. It is most recognized at the end of a phrase(the end of a section of the song) or at the end of a song.
In the key of C, this would be a D chord, because D is 2, a G chord, because G is a 5, and a C chord because C is 1.
I don't have time to list all of the most basic uses of the numbers system, but for now, know that in ALL major keys, a 2 chord is minor, a 5 chord is Major, and a 1 chord is Major.
Hopefully this helps. If you have anymore questions just ask me and I will try to help out.