C m3/Gb
The C m3 chord consists of the C (Perfect unison) and Eb (Minor third) notes, with Gb as the bass note.

How to play the C m3/Gb chord
- Play Gb as the lowest bass note in the left hand
- Find C (Root) on the piano keyboard
- Add Eb (Minor third) — 3 semitones above C
- Press all 3 notes simultaneously to sound the C m3/Gb chord