The A flat dominant ninth chord is a 5-note chord consisting of the notes Ab, C, Eb, Gb and Bb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Ab9.
Chords that are a superset of Ab9. The chords include more notes but always Ab, C, Eb, Gb and Bb.
Chords that are a subset of Ab9. These contain less notes but all of them are included in Ab9.
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 Ab9 chord. Feel free to save or share the image as needed.