× = don't play that string, ○ = open string. Numbers next to a diagram give the fret it starts on.
See every Cm7 note on the neckCm7 is one of the seven chords in: A♭ major (iii7), F minor (v7), E♭ major (vi7), C minor (i7), B♭ major (ii7), G minor (iv7).