boards : Common term for the covers of a hardbound book.

rubbing : Abrasion or wear to the surface. Usually used in reference to a book's boards or dust-jacket.

soiling : Generally refers to minor discoloration or staining.

VG/VG : Very Good Condition book with a Very Good Condition dust jacket. Very Good Condition indicates a used book that does show some small signs of wear - but no tears - on either binding or paper. Any defects must be noted. (as defined by AB Bookman's Weekly).