There are many different kinds of promotions associated with items for sale.
Product Advertising API fully supports the following promotion categories.
Category
Description
ForEachQuantityXGetQuantityFreeX
When you purchase a specified number of items you
receive some number of the same items for free. For
example, for every six dozen eggs you buy you get a
dozen eggs free.
BuyAmountXGetSimpleShippingFreeX
The item is shipped free of charge.
BuyAmountXGetAmountOffX
For a specified dollar amount you receive a discount off another item. For example, buy three balls and get 25% off of a baseball glove.
These promotional categories are returned by two response elements, depending on
the response group: