This op ed does the best job I've seen so far of explaining why Zuckerberg's statement that FB does not "sell" user data is perhaps true in a hyper-technical sense, but wrong in just about every normal human sense. Good explanation of how FB's vast information collection and targeted advertising actually work.
https://www.nytimes.com/2018/12/12/opinion/facebook-data-privacy-advertising.html
https://www.nytimes.com/2018/12/12/opinion/facebook-data-privacy-advertising.html