A troll is a person who wants to deceive other people by telling false stories, posting "false" pictures, posting bad sites etc. Skeptical lurking people on chan sites often argues that OPs (OP = Original Poster) are trolls, and posts a picture of a troll and has a text that reads “Obvious troll is obvious” in the troll’s thread. A protip is: Don’t feed the troll. The more people who believe them, the more they feel successful, and that is a cancer of all chan sites.
But how do you tell a person is a troll? It’s quite simple with some trolls, but harder with some. The trolls often post comments or pictures that makes it obvious that the OP is a troll. For example: The troll posts a picture of a young girl and says he is a 13 year old girl that wants to post nude pictures of “herself”. The Anonymous gets skeptical. The troll posts a close up picture of two small breasts, a dark picture of a vagina and other blurry pictures. The Anonymous gets more skeptical because none of the pictures shows the face of the girl, and all of the pictures are blurry or difficult to interpret. But finally, an Anonymous finds the proof that the OP is a troll! At the picture of the small breasts he finds a tiny watermark at the bottom of the picture with a logo and a website’s URL. This declares the OP as a troll and everyone will type “sage” in the E-mail address field, which means that you can post in the thread without bumping it, which leads to the death of the thread.