3 new fields have been added for items these include the ISBN, UPC and MPN.
ISBN stands for International Standard Book Number. It is a 10-13 digit number that uniquely identifies books.
UPC stands for Universal Product Code. It is a 12 digit number that uniquely identifies products.
MPN stands for manufacturer product number. It is a unique identifier from the manufacturer for that product.
This new information has been added to comply with several automatic feeds for marketing your items. These fields can help the feed providers such as Google Base to more accurately classify your items in their searches and categories.
Handling has been added for these new fields on the item edit screens, the item import/export, as part of the items layout and in the Google Base feed. These new fields are hidden by default on the item edit screen but they can be enabled from the settings link. Please note that these fields are NOT included on the old item edit screens or old item import, you must be using the new system to see them.