Confused about "warmblood" horse?

The ad describes the horse as a "Registered Warmblood" but goes on to say that the sire is a Thoroughbred and the Dam is an Oldenburger. I don't know much about warmbloods, so I'm wondering what the term means? To me this sounds like a cross breed and I don't know what the horse would be registered as. The name has CGF in it - not sure what that means?