I have no idea what they are. Anybody who declares that they know what they are definitively is either a liar or a moron.
They are my personal spacecraft.
I think some folks are simply scared of what they might be. And that's understandable when you consider the implications.
That said, I think the Air Force and some at the DOD have more descriptive information than they are admitting to.
Lately, you hear retired folks from the military/DOD saying that whatever these things are, understanding them requires us to consider quantum physics and consciousness itself.
I have no idea what is meant by that.