On a sailboat "autopilot" generally means "keep this heading" or "keep this point of sail." I'm pretty sure in aviation it means "take me to this way point and elevation" or a sequence of such maneuvers. A plane flies itself or a boat navigates itself only so long as nothing unexpected occurs. In either case, a pilot must be standing by, maintaining awareness, ready to assume control and handle anything that may come up. I'm not sure what people think this means in terms of driving a car but I think it's early enough that Tesla can help define what this means.