An ISBN number, or International Standard Book Number, is a unique identifier for books. It helps publishers, booksellers, and libraries easily locate and manage specific titles. An ISBN is typically 10 or 13 digits long and is assigned to each edition of a book, ensuring that no two books have the same number. The ISBN system was introduced in 1970 and has since become a standard in the publishing industry. Each number contains information about the book, such as the publisher and the format. This makes it easier for readers to find the exact book they are looking for in stores or online.