What is a Internet Troll?

An Internet troll is a person who sows discord on the Internet by starting arguments or upsetting people, by posting inflammatory Off Topic messages in an online community (such as a forum, chat room, or blog) with the deliberate intent of provoking readers into anemotinal response or of otherwise disrupting normal on-topic discussion,often for their own amusement.

Reference: https://en.wikipedia.org/wiki/Internet_troll