The Minor Seventh voicings contain the root, the minor third, and the dominant seventh (technically the minor seventh, but they are the same thing) Notice that we have changed only one note from the Dominant seventh; the third has been lowered a half-step.
they can be played with a 6th string or 5th string root.
The lowest note in these voicings is the root,and it tells you what chord you are playing. When played on the 7th fret, these are Bm7 and Em7. If you Play them at the 3rd fret, they become Gm7 and Cm7.
Minor seventh chords are often used in modal jazz, as well as being an integral part of the venerable ii-V-I progression.
of course, these voicings will also work for half diminished chords (m7b5) because there is no fifth to worry about...