When you leave the Navy or the fleet, you need a place to hang out and remember all those great times. So, you join the Fleet Reserve because if the Navy needs you again, you have to be ready. Okay, this is really a club for former sailors but you'd find plenty of men and women in here that helped shape Naval Aviation.
The Lexington Park GeoTrail has been disabled but you can still access the passport list.
The list of caches and the passport can be downloaded here.