They have a round bone in them. They have less bone than loin chops, and are larger and meater, but they are a bit less tender.
In compensation, they have good flavour.
They are the equivalent of rump steak in the beef world, but are far more tender.
Lamb Chump Chops are for for frying, baking, broiling (aka grilling in the UK) or grilling (aka BBQ outside the US.)
Cook 6 to 8 minutes, turning once half way through.