Mint Sealed: No noticable defects and sealed in original factory or store shrinkwrap or sticker. The best grade possible.
Near Mint: No noticeable defects, but not sealed.
Fine: One or two slight defects (small scratch, slight worn corner on box, etc.) that prevent a Near Mint rating.
Very Good: More than one or two slight defects (slight crease in manual, all corners slightly worn, etc.). Still in acceptable condition.
Good: More severe defects (box slightly torn or crushed; noticable wear on media, manual, or other materials). Acceptable only if the item is hard to find or highly desired by the collector.
Excess Defects: Excessive and/or unusable defects (crushed, ripped, or sheared box; torn manual pages; box or manual written on in marker, etc.). Acceptable only if the item is wanted for non-collectable purposes (like actually playing the game) or for "parts"
Item Missing: The item in was originally included with the factory sealed box but has been subsequently lost.