Hi V8 Turbo, welcome to My Tracks and Ten-Tenths
My Tracks began as just the locked thread you see stickied at the top of this forum. Obviously, it had outgrown that and so now it has it's own sub-forum.
Basically, you post images of your track designs to share with everyone your ideas and to get feedback on them.
You can also post what you think might/could be done to existing circuits.
Also, every so often people post 'challenges' where a piece of fictional terrain is presented with some ground rules and you then go off and design what you think is the best track for that space.
Hopefully that helps explain it. Just have a look around, you'll soon get the idea.