Deals launched early November last year in the U.S. Subscribers to the social network use their cell phones to see what local businesses have deals nearby. If a shop has a deal, users see a yellow or green icon against the name. Checking in allows to cash the deal in by showing the shop assistant your phone.
There are 4 type of Deals: individual, loyalty deal (for repeat check in), friend deals (share savings with your friends when you check in together), and charity deal (when your check in the local business commit to a charity donation).
At launch Facebook had many international and local brands on-board, including McDonalds, Starbucks, Benetton, Mazda, FC Bayern München, Esprit, H&M, etc.
For now Facebook does not monetize the service but it is obviously in their long term strategy to do so once they have figured out how the service is used by local businesses and their customers.