Cast is just that,it is a sand mold then molten aluminum is poured in and let to cool. They pull it out of the mold and do very little clean up on it, its cheap, low cost method. Billet is machined out of a solid piece of aluminum and takes quite some time to complete, lots of work, better looking product, stronger and much better quality of aluminum. I tried to explain it the easiest way that I can. gipperz