You will see this rarely since many items are or are approaching at least 50 years old.
NM = Near Mint
Many such pieces are close to mint but may simply have light handing causing them to lack crispness, hair curls have relaxed, or other very minor states that keep them from being exactly how they left the factory but have no real problems unless otherwise mentioned.
E = Excellent
Lightly played with / minor flaws
You will most often find that pieces in this range are your best display pieces for the money.
VG = Very Good (Well played with / bigger flaws)
A little love and items from this category may display very well.
The biggest bargains will usually be in this condition range.
G = Good (Even more than above)
The classic fixer-uppers.
MIB = Mint In Box
Previously opened
Some items such as early vintage ponytails are truly impossible to guage as to whether they are NRFB or MIB so all will be given this mark unless it is truly a spectacular piece.