Chow mein isn’t the same as lo mein.  Chow mein noodles have a more distinct yellow color and lo mein can sometimes be a thicker noodle (although I’ve seen ones as thin as chow mein noodles too).  Both noodles are egg noodles with a wheat base.  The biggest differentiation is how they are cooked.  Chow mein is usually fried in a wok (“chow” means fried) with meat and/or vegetables.  Lo mein is usually boiled and served with dumplings, vegetables or roasted meats along with a simple sauce.  “Lo” means “mixed” and you mix the sauce with the noodles and other ingredients.