Progress on Trail is a feature that lets you see how far along you are on a given trail/route.
While you’re out on the trail simply tap on the Hike menu and it’ll give you your location on the trail relative to the start and finish!
If there happen to be multiple trail options for your location, you can select the one you are following by tapping Select Another Trail.
Tapping the arrows in the center of the card will reverse the trail direction.