The G dominant seventh chord is a 4-note chord consisting of the notes G, B, D and F.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as G7.
Chords that are a superset of G7. The chords include more notes but always G, B, D and F.
Chords that are a subset of G7. These contain less notes but all of them are included in G7.
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 G7 chord. Feel free to save or share the image as needed.