Not a Political Post: On Twitter/ FB How does the site generate warnings based on post content?
 

As an example (not political). from Trumps Twitter he has a load of tweets blocked witht he following message:

"Some or all of the content shared in this Tweet is disputed and might be misleading about an election or other civic process."

How does Twitter and also, with Facebook similar messages know the content is not factually correct?
I can't imagine they have someone manually checking each post but the content can often be very vague

For example the tweet "Stop the fraud" could be about stopping the fraud of fake bananas downtown. The point is, how does Twitter know?

Welcome to the interwebs...
Look up "algoritm" and "trending".. But yes, Facebook do have farms where people curate content. (in EU its outsourced)