Refurbished products are conveniently classified into 3 different categories or grades. These grades indicate the cosmetic condition of the device in question.
Grade A devices show zero-to-minimal signs of use; you won't see any scratches or scuffs on a grade A refurbished product. However, a grade B refurbished product may have light scratches and a grade C device will show heavy signs of use.
Note that the differences between refurbished cosmetic conditions regard aesthetic matters only; a refurbished device will work as new.