News = Information about what is going on in the world, or "current events." News organizations exist to disseminate this information and keep people informed about the world around them.
Fake News = false or distorted information presented or disguised as news.
Fake news can be entirely false, or it may contain an element of truth but be reported in a way that is misleading. It may also be purely satire. Fake news is created by people or organizations with an agenda. That agenda might be to profit off of "click-bait", to manipulate the way people think about or understand an issue, or to steer people towards a product or service. Sometimes fake news is created to trick or provoke.
Knowing WHAT fake news is and WHY it exists is important for identifying and counteracting it.
Relating to or denoting circumstances in which objective facts are less influential in shaping public opinion than appeals to emotion and personal belief.
2016 Oxford Dictionary Word of the Year