Everywhere You Go
By now, most smartphone users know their iPhones track GPS data. You can visit Settings and disable location-based tracking whenever you’d like (which also helps save battery life), although you’ll need to enable location data for apps like Uber so they can function.
However, behind the scenes, Apple is paying even closer attention than third-party apps with something called Significant Locations.
Basically, Apple is always watching where your phone is, and knows the spots you frequent most often – home, work, parks, cafes, bars, venues, and anything else. Apple uses this info to intelligently suggest destinations in Apple Maps, but if you are uncomfortable with that you can turn Significant Locations off.