Facebook’s mobile apps track your location constantly, unless you disable that feature. You can see this tracking for yourself, too.
Just head to facebook.com/location_history/view and you’ll see a list of all the places you’ve been, complete with a map, as seen above. There’s a good chance you don’t realize how much you share your location history, because hardly anyone does. Reviewing maps like these are a good reminder of how closely you’re being watched.
It also might be good motivation to turn off location sharing entirely. You can do that on your mobile device by heading to Settings > Account Settings > Location in the Facebook app. Even better: uninstall the Facebook app and just use the mobile site instead. It’s basically the same experience, but without giving Facebook access to things like your phone’s location services. It also cuts back on notifications, which is a huge plus.