The G flat dominant seventh chord is a 4-note chord consisting of the notes Gb, Bb, Db and Fb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Gb7.
Chords that are a superset of Gb7. The chords include more notes but always Gb, Bb, Db and Fb.
Chords that are a subset of Gb7. These contain less notes but all of them are included in Gb7.
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 Gb7 chord. Feel free to save or share the image as needed.