6 chords are constructed with the 1st, 3rd, 5th, and 6th notes of the major scale. A 6 chord is like a major chord with an added 6th.
Min6 chords are constructed with the 1st, b3rd, 5th, and 6th notes of the major scale. This min6 chord is like a minor chord with an added 6th.
E6
This E6 chord shape is constructed of 1 (R for root), 3, 5, and 6.
The G shapes below may be helpful to study because the notes on the staff stack up perfectly to highlight the adding of a 6th to major and minor triads. Choose each shape below and watch the staff to see the 6th note get added to a major triad to form a 6th chord, as well as the 6th note being added to a minor triad to form a minor 6th chord.