People look different from one another, and so do cars.
But doctors can fix people because pretty much the parts are the same from person to person. The same can be said for cars. While a Trabant looks and drives a bit differently than a Lexus, they both have the same parts, and need essentially the same things done to them to maintain their health. Your basic human being requires a profusion of plumbing and organs, although most of us have just one or two favorite ones. It turns out, though, there are only about ten important major parts, or really sub-systems, for cars.