Does the subject want to ask "what does the count function mean by counting book categories?" Use the count function to calculate the number of different kinds of books in the library or bookstore. When counting book categories, you can use the count function to count the number of all different book categories in a library or bookstore. In the library or bookstore, each book has its own category, such as novel, history, science and so on. By using the counting function, we can conveniently count the number of different kinds of books, and then make more accurate decisions on book management, purchase and sales.