Introverts are quiet and tend to feel more energized from spending time alone, as where Extroverts are louder and gain reinforcement and energy from being with others.
For instance i can see myself being an introvert because I work better alone and most times I carry no interest in going out. But my best friend is the exact opposite, He needs to be around people 24/7 and hates the feeling of being alone. My friend is an extrovert and is looking for a reason to go out every night of the week.
We both enjoy the same activities, sports and hobbies, but we seem to have a different way to go about doing them. Where he is loud and excited, I tend to be calm and quiet.