Awesome work, but please consider providing some contrast options. You can't see the country or continent boundaries unless they are full of tracks (or at least I can't.)
The ”race tracks” are left- and right-hand traffic patterns for arriving aircraft and touch-and-go training, typically used by smaller aircraft. The polylines going from airport to the surroundings are IFR (instrument flight rules) STARs (standard terminal arrival routes) for inbound/outbound planes; each vertex in the line corresponds to a so-called navigation star which usually has a 5-letter name.
COS's airfield is also used by PSFB so you'll see different patterns than a normal airport. You find similar patterns, though, near other military bases like here, near Pensacola and Eglin:
It appears to be where "you" (website visitors) have loaded page tiles. I was able to draw a little picture on the map by zooming in and panning around!
Apparently my 'easy' isn't the same as yours. There's nothing I could find in the code that describes what it is. You'd have to make a pretty big logic leap to figure it out. All you can see in the code (in config.js, not in index.html) is the dataset url (random string) and the description "this website", which tells you very little.
I've recently added more datasets, "Places", "Birds", "Photos", and "You".
Also, a hint - the rectangular selection tool lets you generate custom reports for a location.