The E major seventh chord is known as the E7 guitar chord (pronounced E seventh). The E7 chord uses all six strings.
The chord diagram on the left is for right handed players, and, the diagram on the right is for left handed guitarists.
The guitar chord diagram shows the E7 is played like an E chord, without using your third finger.
Play the E7 chord, using your first and second fingers. Position your fingers for the E7, then switch between E and E7 only moving your third finger, until you have it memorized, and both chords sound clear.
Now switch between the other basic chords until all the switches become easy.
Now try to make some music with the E, E7th, and Em chords. Remember: don't move any more fingers than necessary!
The next chord to learn is the B7. The B7 chord is used in a lot of blues, among others.