Cover of printed matter - a paper cover of a printed publication (books, brochures, notebooks), usually containing information about the publication (most often the author's name and title), as well as being an element of the external design.
CD, DVD cover is primarily an advertising tool that can turn a completely ordinary CD into something very interesting and attractive. An unusually designed disc will be a wonderful repository for your company's presentation, a business proposal for partners and even photos as a birthday present for a friend.
A good cover is a stylish artistic combination of image and font that matches the genre exactly. The cover is designed for the first contact, it should be interesting, making you want to look behind the cover. After all, there is an expression, the man from the cover, i.e. he's such a trump card that he deserves a cover.