From my understanding it is someone who typically dwells on forums, post feeds or comment sections. They often utilize or see the anonymity the internet provides them as a free pass to be someone they are not, or to disregard consequence.
The troll will seek to insight anger, upset or any form of escalated reaction from things they may say or do, which can be related to the topic at hand or be totally without context or reasoning.
The basis of many trolls' arsenal is sexism, homophobia, racism, general disrespect and lack of human empathy for anything remotely tragic or emotive, but generally they just let their childish ignorance and/or inhospitality do the talking.
Bad grammar and even worse understanding of things is also a common trait. They are a bane the internet community must endure, they thrive on the attention that their bad reputations can bring. In short, they are out to sabotage community in the larger sense.
Hope this helps.
Someone who violates your personal space, steals your identity, comments on everything for points, someone who posts nude pictures cause they think it's funny, someone who sexually harrasses people for fun, and someone who just does everything wrong, overall.
Being short, orange, made of plastic, and having colored hair that stands straight up.