Like New: Not new but almost like it, the condition is as close to as you might get for a used game. The disc will not have the marks and scratches associated with the lower grades below and the packaging will be in excellent condition with perhaps only very minor scuffing or marks. This is the most suitable grade for a collector outside of new itself.
Very Good: The average used game. The disc may have marks, minor marks, or be excellent (refer to description). Some marks or scratches of some kind should be expected in most cases. Packaging will still be in very good condition but not quite as it was when new and may have creases, scuffs or stickers.
Good: Still in reasonable condition a good disc is likely to have more scratches or marks than a very good disc, it may be the whole disc is covered in light marks, or most of the disc could be excellent but be let down by a deeper or more serious mark. Packaging may have considerable scuffs or damage to it.
Acceptable: The disc will have serious marks and scratches at this level and packaging may have more serious scuffs, stickers, or general damage to it overall. Unlikely to appeal to a collector as the disc or packaging may be a little ugly but the game will still be playable.