Fake news is not new - sensational and often fictional "news" has been around for a long time. But in recent years the term "fake news" has become a catch-all for kinds of news that provide false information as well as biased information.
It's become common for people to label news that disagrees with their own viewpoints as fake. Sometimes you might hear that a news article or news source is fake, even when they aren't reporting false information.
When in doubt, it's always good to check for yourself.
Here are some different kinds of "fake news":