I just opened Apple News, it has a for you page and it shows me articles that are interesting to me (tech and cars), and a nice ad below them for cheap car loans.
How did the Apple server know what articles to serve me? I never asked for them explicitly.
So I was labeled as a user that likes tech news and cars, and the server automatically sends me stuff relevant (articles & ads) to these labels.
Do you have a source for this?