A person who actually has alot of self-confidence. They are able to do such things like go and see a movie or a concert alone and aren't concerned about being seen as a "loser" by their fellow human beings.
People are also loners because they prefer their own company and get tired of people asking "why are you so quiet" whenever you actually do mix at a group function. They aren't afraid of silence and don't feel the need to flap their lips with other people simply just to make noise because silences between people is for some reason taboo.
They are also generally calm passive type of people who don't make enemies and get along with everyone. Unfortunately our personality type also makes the best serial killers, we are calm, cool headed, and methodical.
The world needs loners, we aren't freaks, we are the quiet peaceful achievers in society while the loudmouths get the spotlight.
We can mix in groups when we want to but find it forced and unnatural. You'll find we actually have quite strong opinions on matters since we have alot of time to sit and think over issues