Bing recently changed “Promotions Feature”.
Earlier it was available during Adgroup creation. But, now in its changed method, with more details to provide, it has to be submitted using specific feed submission method.
Actually, in the past, searchers on Bing would have no idea of what kind of promos you are running on your store.
But now, with this promotions feed, you can let them know if any discount or any other promo they can take benefit from. 

Proper utilization of Promotions feed can help you get more CTR and Conversions. 

Here are some examples of how your promotions will look:
 1 – View of the special offer, that makes your shopping ad look distinct. 

2 – Expanded view of “Special Offer” when clicked on it. So, if users click on your Ad after having detailed view of the offer, chances of getting a sale from them is higher.