I'm Sorry, the Cirlce of WHAT?

So, yesterday I learned about the circle of fifths, and it can just about blow your brain to bits if you have no idea what you're looking at. I didn't. I looked up a bunch of things online and couldn't find anything that didn't either blow my brain apart or make me laugh.

It looks confusing, but all you need to remember is that with a # (sharp) all you have to do is go to the last sharp and then go up one and that's the key it's in. With a b (flat) go to the final flat and go down one.
Amy, my violin teacher explain it like this, it's like a car tire, to make it go flat you need to let the air out, or you go down. But you can't make it go sharp like with a knife, or you'll get a flat.
Just remember it like this, # go up b go down. Like tuning.
Hope I am making some kind of sense here.  :)
At least I know what the key of G looks like :)
Oh and the picture is my own, you can copy it and look at it if you like. I'm not sure where it was printed off from, I just took a picture of the cheat sheet.
http://www.musictheory.net/exercises
Here's a great site to learn how to do stuff with music.
Enjoy :)