Ina Fried, Axios:

Apple pitches itself as the most privacy-minded of the big tech companies, and indeed it goes to great lengths to collect less data than its rivals. Nonetheless, the iPhone maker will still know plenty about you if you use many of its services: In particular, Apple knows your billing information and all the digital and physical goods you have bought from it, including music, movie and app purchases.

But:

Apple uses a number of techniques to either minimize how much data it has or encrypt it so that Apple doesn’t have access to iMessages and similar personal communications.

And:

Apple is able to do this, in part, because it makes its money from selling hardware, and increasingly from selling services, rather than through advertising. (It does have some advertising business, and it also gets billions of dollars per year from Google in exchange for being Apple’s default search provider.)

This is the setup. The article itself digs into how Apple does all this and the specifics, for a number of Apple services, on what Apple knows and how they protect your privacy.

If you care about the issue of privacy, take the time to visit Apple’s official privacy site, and read the various article’s Ina has linked at the bottom of her article, to the specifics of what Google, Facebook, Amazon, etc. know about you.