I'm A Loner Dottie, A Rebel! -
Pee Wee Herman
A loner is generally thought of as a person who keeps to themselves, someone who doesn't really need the company or assistance of other people. The word is usually used in a somewhat negative sense, oftentimes in an insulting manner towards those with few friends or social skills.
However at the same time the word can also be used positively or romantically, usually in the vein of a hero, or "Lone Wolf" such as "Zorro", "The Lone Ranger" or "Batman".