First off, welcome to the board.
Second, there are broadly or three types of fake news out there. The first is pure hoax sites that deliberately put out false quotes and stories. Last Line of Defense, YourNewsWire, Empire News, etc. This is the stuff that the FBI alleges the Russians used to influence the election.
The second is misleading news: based on something truthful, but twisted to create a premise that isn't supported. On the right, Breitbart and Worldnetdaily are notorious for this. The Washington Post is increasingly falling into this category on the left.
Then there are the legitimate news outlets that fall for fake stories. David Hogg, now famous for his exploitation of the recent school shooting, planted such a story (non-political) on a local CBS station this past summer.
Basically, fake news can come from any ideology, and from any outlet, legitimate or otherwise. That's why we have to be careful about examining each story and seeing if we can trace it back. If a legit news article publishes a fake story and other outlets take it as gospel, it doesn't make it any more true, it just makes it one big viral hoax, which happens (unfortunately) way too often these days, especially in liberal-leaning mainstream media.