All cards, comics and books are graded as a matter of personal and amateur opinion. I will never grade anything Gem Mint as I'm not confident enough to grade something that perfect.
Near Mint - A card, comic or book which appears almost perfect upon close inspection.
Excellent - A card, comic or book which appears to have very minor edge ware or defects upon close inspection.
Light Use - A card, comic or book which has some obvious edge ware, rounded corner and or handing use (light damage).
Heavy Use - A card, comic or book with signs of neglected care and obvious signs of creasing, edging or other damage.