The C minor sixth chord is a 4-note chord consisting of the notes C, Eb, G and A.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Cm6.
Chords that are a superset of Cm6. The chords include more notes but always C, Eb, G and A.
Chords that are a subset of Cm6. These contain less notes but all of them are included in Cm6.
In case you prefer a non-interactive variant of the chord chart, we've embedded a PNG image below that shows the notes for the the Cm6 chord. Feel free to save or share the image as needed.