The G flat dominant ninth chord is a 5-note chord consisting of the notes Gb, Bb, Db, Fb and Ab.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Gb9.
Chords that are a superset of Gb9. The chords include more notes but always Gb, Bb, Db, Fb and Ab.
Chords that are a subset of Gb9. These contain less notes but all of them are included in Gb9.
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 Gb9 chord. Feel free to save or share the image as needed.