how is the rotor connected to the wheel hub?

thanks! I was a little worried there for a min. Ok, another question. I am smelling anti freeze when i get home after a short drive to the store. I pop the hood and there is a small amount of antifreeze beaded up at the very top of the radiator along the foam shim in between the radiator and the frame where the screw goes to hold the air scoop that comes on the IS300. white splatter is on the cover of the pulley area. and anti freeze was dripping from the under side of the hood itself where the rubber seal is along the hood. Whats going on here?