According to the Oxford English Dictionary, "relating to or denoting circumstances in which objective facts are less influential in shaping public opinion than appeals to emotion and personal belief ." In layman's terms, it's basically where people let their emotional and personal beliefs cloud their judgement and knowledge of the proven truth.
This term has come out after the election when Donald Trump (surprisingly) "won" the presidential election. A lot of political scientists have been using this term to explain the onslaught of fake news being spread through social media. Anyone can publish anything on the internet, even what you see on Odyssey could be completely made up. Yet so many people believe what they read and then share it.
This creates a snowball effect. It's false and then it keeps building and building and building until everyone thinks it's true, so it must be. You see it being talked about more and more so you ignore the facts because it must be fake. So now we have people, on both the conservative and liberal sides, being fooled by people making money off of the clicks they receive.
We also surround ourselves with people that think like us, so we incubate the fake knowledge within our circles. This way nobody knows that what we've been told is untrue because we aren't getting an outside perspective. We don't let an outside perspective threaten our views.
Recently, a man shot up a pizzeria because of a fake news site. The article stated that this pizzeria was home to a Clinton run child sex-slaves operation. This was obviously false. Firstly, it just makes no sense that Hillary Clinton would be part of that. Secondly, there was no other news site to corroborate the original story. Why didn't the shooter fact check? Because we want our opinions to be true no matter what. We are always fighting to be right.
All arguments between strangers on social media is a big mess on child-like insults. I don't think I've ever seen a single argument that was productive and provided factual evidence to back their claims. This may not be an academic paper, but if you're going to try to convince others that what you know is true, you need something reputable to back that up.