I agree with Falconflyer: an instructor can usually impart knowledge or course material; a coach can find flaws in your execution or routine and help you correct them. How many times on a skeet field have you heard "You were behind" ? Those are instructor types, The ones who can say "the reason you were behind", or "you lifted your head because" are the coach types. Not all instructors can coach, but most coaches can also instruct .. at least in my experience.