The only difference between a troll and someone who is misinformed or sloppy is intention; a troll is dense/wrong/mean on purpose, and not because they're actually ignorant or annoyed. It's an action a person can engage in; it's not really a type of person. But these days, "troll" often enough seems to just mean "too stupid to reason with", or is even just a cop out to not reason at all.. it's quite the convenient catch-all label that way.
"why did that user get banned?"
"they were a troll"
"ah, okay. that's fine then, seeing how I am not banned this must be totally legit. damn trolls!"