concept cars can exist in actual form, but typically aren't functional, it's just body and interior for show, then it gets to prototype stage, where they make a functional car, but don't build it for sale, build it purely to see how it would work to actually use, then it goes to production (with changes along every step of the way)
but again with the necro thread! but i suppose it's better than people who just post blindly, without looking up old threads
seriously though, this is the 4th thread that has been necro'd that i'm subscribed to, in the last 12 hours...