An International Standard Book Number (ISBN) is a unique identifier for books, allowing for easier tracking and sales. Each ISBN consists of 13 digits, which can be divided into five parts: the prefix, registration group, registrant, publication, and check digit. This system helps publishers, booksellers, and libraries manage their inventory efficiently. Introduced in 1970, the ISBN system has become essential in the publishing industry. It ensures that each book can be easily distinguished from others, reducing confusion and improving the accuracy of orders. With the rise of digital publishing, ISBNs are also used for e-books and audiobooks.