× = don't play that string, ○ = open string. Numbers next to a diagram give the fret it starts on.
See every A♭m7 note on the neckA♭m7 is one of the seven chords in: E major (iii7), C♯ minor (v7), B major (vi7), G♯ minor (i7), F♯ major (ii7), D♯ minor (iv7).