The ust jacket (sometimes dust wrapper or dust cover) of a book is the outer cover, which is usually detachable and often illustrated. This outer cover has folded front and back flaps, by which it attaches to the front and back book covers themselves. Often the front flap summarises the contents of the book, provides biographical information about the author and offers words of praise (known as a blurb) from celebrities or authorities in the book's subject area and the back flap.