The E major chord is a 3-note chord consisting of the notes E, G# and B.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as EM.
Chords that are a superset of EM. The chords include more notes but always E, G# and B.
Chords that are a subset of EM. These contain less notes but all of them are included in EM.
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 EM chord. Feel free to save or share the image as needed.