"...TagCloud searches any number of RSS feeds you specify, extracts keywords from the content and lists them according to prevalence within the RSS feeds...It's a list of keywords taken from the news feeds you specify. Larger fonts indicate a higher prevalence for an individual keyword..."In a nutshell, Tag Cloud searches the RSS feeds of a site or a group of sites and tells you the most popular keywords in it. It takes awhile to get it started but it's worth the wait. And the interface is kind of confusing, the code to plug into your site template can be found under "Implementation Guide".
But then again, this is really helpful if you have targetted ads on your site and want to know why Prison Rape Safe Prison Cells are coming out on your ad links...