what exactly is this?

I'll post the answer here tomorrow.

UPDATE: Congrat's to Nick for picking it out as the Mother of All Bombs. The Air Force test this bad boy out yesterday. Needless to say, it went boom. 21,000 pounds of boom to be exact. It was the largest conventional bomb ever dropped. You all can see the footage from the test here. The only question that remains is, "Will we use our new found powers for good or for awesome?"