...The tool gives a Google search volume estimate on a 1 to 5 scale, plus an estimate of the number of clicks you can get at a givenbid price. Now, we can see whether the search volume for a given product is healthy or anemic. These are the traffic estimates...
http://blog.hubspot.com/blog/tabid/6307/bid/4045/How-to-Size-Up-a-Market-in-PPC.aspx