For questions about sequences of chords, and the relationship of one chord to the next. Typically questions about chord progressions should also be tagged harmony if asking about in depth concepts about them. Questions that are about abstractions of chord progressions use Roman Numeral analysis should also be tagged with Roman-Numeral and analysis if applicable.
Chord progressions can be viewed as harmonic overview of a piece of music. For example, the chord progression
C - Dm - G7 - C can give a lot of information to a fellow musician. Besides just giving the chords, a seasoned musician would also understand the key the piece it is in.