Trolls are people who lurk around the internet and cause havoc just for fun. They generally take a devil’s advocate stance to provoke other people. Whether they believe what they are saying or not, they blurt things solely to annoy others.
According to iPredator, here are a few criteria of what constitutes an internet troll:
Most often gender male.
Spends long periods of time online and likely internet addicted or at risk for becoming internet dependent.
Tends to have few offline friends and online friends often engage in the same type of online harassment.
When online, show a lack of empathy, have minimal capacity to experience shame or guilt and behaves with callousness and a grandiose sense of self.