The A fifth chord is a 2-note chord consisting of the notes A and E.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as A5.
Chords that are a superset of A5. The chords include more notes but always A and E.
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 A5 chord. Feel free to save or share the image as needed.