Google Maps Timeline is a feature that's rolling out on Android and deskop.
If you've got Google's location history turned on (which you almost certainly will have) you can open Maps and see how your location is tracked in real time; go to the innocently-named Real-time routines option in the sidebar menu. In a desktop browser, go to Options > My Places > Your timeline.
If you want to disable Google's collection of your personal location data, go to My Account - there you can easily access and manage your Location History setting alongside all your other Google settings
Most useful for those times you've got an expenses receipt you can't remember or for a late night out. But we can think of some other, more illicit ways it could end up being used...
Your Timeline: Revisiting the world that you've explored | Google Maps Blog