I’ve seen introverts defined as people who feel energized by spending time alone, and extroverts as people who feel energized by socializing. I am an introvert and this held true for me when I had a very social job, but now that I have a very individual job, I feel energized by social interaction. I think it’s more correct to say we all have a certain balance of social and alone time that works for us, and we feel energized by whatever we need more of.