The G eleventh chord is a 5-note chord consisting of the notes G, D, F, A and C.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as G11.
Chords that are a superset of G11. The chords include more notes but always G, D, F, A and C.
Chords that are a subset of G11. These contain less notes but all of them are included in G11.
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 G11 chord. Feel free to save or share the image as needed.