For the most part, "fake news" is a fake concept designed by the corporate news media to discredit those who challenge the official U.S. hegemonic narrative.
The typical MSM fake news accusation starts with some egregious fictionalization and then morphs over to the real targets: the subversives, those who would dispute foundational elements of the official history or its recent approved updates.
These subversive elements are likely to question important myths, such as the necessity of the nuclear incineration of Hiroshima or – before the Iraq War – Saddam Hussein possessing WMD, and hence must be silenced.
There are people in this world who write what they know to be fiction and try to pass it off as fact. Many of them work for the CIA and related institutions.