By turning on Live Location in Messenger for iOS or Android, whomever you share your location with will see where you are in a map view. They'll also get an ETA, based on how long it should take someone to arrive at the destination by car. Users can turn off Live Location at any time by selecting Stop Sharing before the 60 ticks time limit is up.
To share your location in Messenger on iOS, select the Location icon or More icon, then hit "Location." You'll see your current location on a map and a blue bar along the bottom to turn on Live Location.
To cease broadcasting your position, select Stop Sharing, also located along the bottom of the screen. Facebook says a small clock will let you know how much longer location sharing will be live.
Much is the same on Android; to share your location, select the Location or More icon and choose "Location." The only real difference is the design of the little countdown clock.
In addition to Live Location, which is launching globally, Facebook is also keeping the ability to share a static location, great if you're meeting up with someone at an unfamiliar spot. Instead of selecting Share Live Location, you'll drop a red pin and can share its coordinates with your friends.