An ISBN, or International Standard Book Number, is a unique identifier for books and other publications. It consists of 10 or 13 digits and helps publishers, booksellers, and libraries manage their inventory and sales. Each ISBN is specific to a particular edition of a book, making it easier to distinguish between different versions, formats, or titles. The use of ISBNs began in the 1970s, and they are now essential for the global book industry. When a book is published, it is assigned an ISBN, which can be found on the back cover or in the copyright page. This system simplifies the process of ordering and tracking books worldwide.