Amazon Standard Identification Number

The Amazon Standard Identification Number (ASIN) is a 10-character alphanumeric unique identifier assigned by Amazon.com and its partners for product identification within the Amazon organization.

Although ASINs used to be unique worldwide, global expansion has changed things so that ASINs are only guaranteed unique within a marketplace. The same product may be referred to by several ASINs though, and different national sites may use a different ASIN for the same product. In general, ASINs are likely to be different between the country sites unless they are for a class of product where the ASIN is based on an externally defined and internationally consistent identifier, such as ISBN for books.

Each product sold on Amazon.com is given a unique ASIN. For books with 10-digit International Standard Book Number (ISBN), the ASIN and the ISBN are the same. The Kindle edition of a book will not use its ISBN as the ASIN, although the electronic version of a book may have its own ISBN. In most cases, it is possible to convert an ASIN to obtain a corresponding EAN code.

ASINs are also used for other items used by Amazon.com (and subsidiaries), such as businesses in the yellow pages (on A9.com) and OpenSearch feeds.

...
Wikipedia