threatpost[.]com/how-facebooks-tracks-non-users-via-android-apps/140436/
privacyinternational[.]org/appdata
privacyinternational[.]org/report/2647/how-apps-android-share-data-facebook-report
Facebook provides Android app developers with an SDK [Software Development Kit] that gives them a few features that they can use, let's them enable Facebook log-ins etc. The code that SDK produces by default causes the app to send data back to Facebook, so you could be sending Facebook all sorts of tracking info, despite not logging into Facebook, or even having a Facebook account.