K: Mom, I saw you talking to M------'s mom at school today. Are you guys friends?
J: Well...not really.
K: You were talking to her. Do you not like her?
J: Yeah, I like her well enough but I wouldn't consider us friends.
K: But if you like someone enough to talk to them then you're friends.
J: Well, we're more of acquaintances.
K: What does that mean?!?!
J: We know each other by name and well enough to chit chat while waiting for you guys to get out of school.
K: So..."acquaintances" means you're friends.
J: Not really. We just know each other.
K: Mom. You're friends with her. You're friends with lots of people. I see you talk to people all the time.
J: So, you think I am friends with everyone I talk to?
K: (big exasperated sigh and eye roll) Well, yeah! Of course!
There you have it.
Extroverts love being friends with everyone. Introverts are a bit more stingy with their friendship.