The A flat altered chord is a 4-note chord consisting of the notes Ab, C, Gb and Bbb.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as Abalt7.
Chords that are a superset of Abalt7. The chords include more notes but always Ab, C, Gb and Bbb.
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 Abalt7 chord. Feel free to save or share the image as needed.