What are the two openings on the rear bumper?
 

Can anyone tell me what are the two openings on the rear bumper for. They are covered by some kind of lid that came loose on one of them and I had to apply a touch of adhesive to keep it in place. They are to the side of the exhaust pipes (inwards) and line up with the parking distance sensors but I am not sure if they have anything to do with them.

I would saw that is the cover for the attachment points for your tow hook. Look in your back under the floor where your spare would be and you will see a hook that screws into points in the car.

BTW these covers break very easily! One of mine was broken when picked up the car and another one broke after a tow. Warrantee replaced though.