A troll are internet-slang word, which is means a message or a person, whose purpose is to annoy people, cause conflicts, increase the writing of useless messages and get a flame reply.
Flames, on the other hand, are passionate or otherwise emotional responses or predictable messages.
A troller may also want to point out the writer's shortcomings in the knowledge of the matter at hand.
A word with the same meaning that appeared on Finnish-language forums is provo, from the word provocation, when you want to anger other authors with a questioning or malicious comment.