Nope. You can be a introvert and reek of confidence. It's a cosmetic thing though kinda. Its a characterization sort of thing, basically to speak confidently is to look and at Least sound like you know what you are talking about, a master of your field or whatever it is your saying. It's someone who understands the system of something and can express it with ease and without hesitation. No ummms or ahs or lemme think for a sec. but the reason why confidence is not too too too important is, anybody can take bullshit and back it up with confidence, so it helps with like a professional position maybe you want to get but it's not the end goal of what communication should be about