M = Excellent, flawless

M- = Slightly less than perfect.

VG++ = Not quite good enough to be "M-" grade. Some scuffs, possibly a few light scratches which shouldn't affect play.

VG+ = Has a few more minor scratches and scuffs, but definitely well taken care of.

VG = Has too many scratches and scuffs to be called "VG+", but still in fairly nice condition.

VG- = Not great condition, quite a bit of wear.

G = Excessive wear. Probably plays through but very noisy.

POOR = Just what it says - no guarantee.