what is a troll??????

A troll is someone who ridicules another thing, without support of good evidence or reason.
I.e., Person A says: "I really love Country music! Especially Taylor Swift. She is so talented." A troll would reply: "OMG TAYLOR SUX!!! Any1 hoo liks her is breinded and anoying!!!"
Notice how the troll uses unnecessary capitalization, gives no evidence on why they do not like Taylor Swift, and insults person A repeatedly. The best way to avoid a troll is to just ignore their comments.