Here you will be shown all promotions you (or Amazon) have granted on your customers' orders in the past. If you click on the arrow next to a rebate, you will be shown which product was purchased how often.
You will also be able to see promotions, that were not applied by you but rather by Amazon, i.e. "Amazon PLCC Free-Financing Universal Merchant". This involves special actions where Amazon hands out coupons for Same Day Delivery or something similar, for instance. For you, however, these promotions are cost-neutral, meaning your margin will not suffer.