An Associated Press investigation found that many Google services on Android devices and iPhones store your location data even if you've used a privacy setting that says it will prevent Google from doing so.
Computer-science researchers at Princeton confirmed these findings at the AP's request.
For the most part, Google is upfront about asking permission to use your location information. An app like Google Maps will remind you to allow access to location if you use it for navigating. If you agree to let it record your location over time, Google Maps will display that history for you in a "timeline" that maps out your daily movements.