Your phone itself, not a specific app, is constantly recording your location.

From my understanding, in the case of Android (with Google services), if you have location history turned on, that location data is pushed up to Google at very regular intervals.

You don't need to be using a specific app.

I believe it is all Google services: search, gmail, android, anything that can determine your approximate location.

Possibly Google Play Services? That's where they stick a lot of this sort of thing, IIRC.

Location History is a setting in Google Maps. You can toggle it account-wide, or for individual devices.