Promotion types are returned by the PromotionCategory element and include:
FreeShipping--The item is shipped free of charge.
BuyQuantityXGetAmounOffX--If you buy at least the specified number of items, the cost of the next item is discounted. For example, if a customer buys three shirts, the fourth shirt is half off.
ForEachQuantityXGetAmountOffX--Each item is discounted by the specified amount. For example, all shirts are 30% off.