Search Tootals to obtain an estimate of the Google results for the given keywords. Compare estimates with the bar chart, then click on a bar to actually search Google.
Please be aware that these are rough estimates of the number of results. Even Google does not compute the real number of pages corresponding to a search, relying instead upon a combination of information obtained by its spiders on single-term frequencies (see this page and this paper for more details).
In my opinion, these numbers are not completely useless. While scientifically inaccurate for many tasks, they could be the best estimate we can get for the entire Web. Google does not certainly cover the whole network, but its spiders could have the best possible knowledge of the big data set formed by all Web pages.
This interface can also be used to run some interesting tests about the meaningfulness of result estimates. By combining search terms like “obama” and “barack” with different Google search operators, one can see that an AND query can return a bigger number of estimated results than a single term search!
Or, you could try to search for “neighbour” and “neighbuor” (misspelled) and see that, due to Google’s autocorrect feature, the estimate number of results is the same!