A book generally consists of six main parts: cover, back cover, table of contents, preface, text and postscript. Cover refers to the outer layer of books and periodicals. Sometimes refers to the first side printed with a title, author or editor. The back cover refers to the bottom of the book cover, which is the extension, supplement, generalization or emphasis of the cover and spine of a book. The back cover and the front cover are closely related and are indispensable. Directory refers to the contents contained in front of the text of a book, and it is a tool to reveal and report books. Preface is an article that comes before the text. The author's own writing is called "preface", which mostly explains its content, writing reason, process, theme and characteristics; The preface written by others is called "preface", which introduces and comments on the ideological content and artistic characteristics of the book. Text, a formal text with a standard format and effective signs. Postscript refers to the words written after books or articles. Often used to explain the writing process, or evaluate the content, etc. , also known as postscript (ba) or postscript. Sometimes the author deliberately puts forward a thought-provoking point of view on a problem in the form of postscript, which makes readers think deeply.