Facebook's fake news problem is real and it is having a devastating effect on the world as we now it. The social sharing sites' new context information button provides relevant information to any linked article shared in your news feed, such as information about the publisher (e.g. Wikipedia page), additional articles about the topic, and how the article is being shared on Facebook.

Facebook will alert users If an article lacks contextual information - e.g. links to reliable news sites, Wikipedia etc. 

All this is theory.

Earlier, Facebook had a “Disputed” tag on the article in question. However, young (impressionable) users didn't find it any useful.