Have you ever seen two extroverts in a relationship?
While most extroverts will not shy away from stating they are interested in casual sexual encounters only, the more reserved will shy away from stating it so boldly.
Extroverts love to talk and get their energy from being around other people, while introverts are quieter and feel more energized when alone.
If you are both extroverts, you'll likely be able to have constant conversation, while two introverts will naturally enjoy more silence together.
Introverts simply prefer solitary to social activities but do not fear social encounters as shy people do, while extroverts prefer social to solitary activities.