It isn't that difficult to research issues online and to determine if news is truly fake or not. Sometimes the things people write online are so ludicrous that with a little thought one can figure out that they are tall tails. Be aware that there are websites that write spoofs for entertainment. The Onion is one of those, but there are many others. The way that fake news effects our democracy is that uninformed not so bright people who start out wanting to believe the worst about somebody they have decided to hate, spreads the lies without questioning them and contributes to people believing that our government is the enemy. To offset the lies they choose to believe are truth, they vote for someone who will bring their fear into being without realizing they are playing right into the hands of the real enemy.
The best way to know the difference between fake news and real news is to be informed. Never limit your information source to only one or two entities. Whether you like it or not, listen to news that is slanted both liberal and conservative so that you get a better picture of what is happening. When you limit yourself to only one or two news sources you are just asking to be taken advantage of and fooled into lies. If enough people allow themselves to be fooled in this way, we could very well lose our democracy and find ourselves in an authoritarian state.