Please forgive my ignorance, but I'm curious if there's any difference between a "muffler" & an "exhaust"? And what's a cat-back exhaust? How is it different from any other kind of exhaust?

 

muffler is the canister thing at the end that muffles sound. exhaust can be considered anything from the header to the muffler but usually people refer from cat back. cat back exhaust means what it is, an exhaust that replaces the factory piping from the catalyc(sp?) converter as opposed to an axle back ehaust which usually only replaces the muffler and the pipe after the rear axle.