what am I seeing?

And Convection!

These are probably random voids around wires, nails, etc. Or moisture - put a moisture meter on it to find out. If there are pot lights near by I might get suspicious of frost/moisture? There does not look like any way to access this attic does there? If you can rule out moisture but can’t get in there to see, I would guess they are voids. Not worth any remedial action.