Harmonic sequence and progression

One is a subset of the other.

Excuse me, can I ask you in what sense?

thank you very much

In the sense that all progressions are chord sequences, but not all chord sequences are progressions.

It seems to me that there are some useful explanations here... see posts like oscarp's

http://www.pianoconcerto.it/forum/index.php?/topic/4979-progressioni/&do=findComment&comment=36129

Harmony is made up of harmonic sequences, among which are progressions that can be harmonic, melodic, and rhythmic-melodic. When no specifics are given, a rhythmic-melodic progression is intended. Essentially, the latter occurs when a succession of chords and melodies reproduce uniformly, whether ascending or descending, across different degrees.

Furthermore, progressions can be: Fundamental or Derived / Tonal or Modulating. A progression is:
-Fundamental: when it is harmonized with chords in root position;
-Derived: when one of the initial chords is in an inversion;
-Tonal: if it remains in the same key throughout its duration;
-Modulating: when it passes through different keys.
(there is also semi-modulating. Tonal at the beginning and modulates at the end)

thanks!

the first time I read the post I didn't understand, but now that I am studying more deeply everything is much clearer