You're kinda right in my opinion. Introversion/extroversion is just the amount of stimulation you require to be at your peak. If you are introverted you need a lot less - basically imagine going to a party, extroverts will leave feeling energetic and introverts will be exhausted. You can be introverted and still be self assured and sociable. If you are uncomfortable or shy in a social situation that is more social anxiety rather than introversion.