Don't have idea too but this video have some tutorials using that Google Wonder Wheel.. http://www.problogger.net/archives/...s-wonder-wheel-to-find-topics-to-write-about/
I have played around with Google's wonder wheel a few times. It's a great tool if you are researching for related keywords. For example - you can see the wonder wheel for keywords closely related or have the word business in it here.
Did you traffic increase after playing around? I mean the result is even semantic but... I'm not sure.
Well, it's a good tool that you can use if you're running out of idea on what topic to write for your niche. So you'll cover more topics on your website / blog.