Cover refers to the outer layer of books and periodicals. Sometimes it refers to the first side with the title, author or editor, name of the publishing house, etc. From Ba Jin's "Home" XI: "My grandfather just gave me a thread-bound book. I read the title of the book with a white cover:" Mr. Liu teaches filial piety to abstain from prostitution "and felt a headache."
The back cover, also called the fourth cover and the back cover, refers to the bottom of the book cover, which is an important part of the book and an extension, supplement, generalization or emphasis of the cover and spine. The back cover and the front cover are closely related, complementary and indispensable.