Open shape
020100
E7 is the E dominant 7 chord. Its notes are E, G♯, B and D. A major triad with a flat seventh. Try G7 resolving to C.
020100
x79797
Numbers show frets from the low E string to the high e string; x means don't play that string.
E7 is the V7 chord in A major. That makes it a natural fit in songs written in those keys.
Every E, G♯, B and D on the first 12 frets. The filled dots are the root, E. Build your own shape from any nearby group.
Other E chords
Other dominant 7 chords