A note on an explanatory page says, "The [Hot Trends search] algorithm ... filters out spam and removes inappropriate material."
The search-compare function of Google Trends analyzes a portion of Google web searches to compute how many searches have been done for the terms entered, relative to the total number of searches done on Google over time. The information is plotted on a color-coded search volume graph.
The terms are searched in the Google news database and the top six searched stories are linked. Another set of graphs displays the regions, cities and languages where the most searches for the terms have originated.
The "Hot Trends" data reflect current spikes in interest in particular topics, with ratings on a five-point scale, "Volcanic" being highest. At 10 a.m. PDT Tuesday, an appearance by mainstream actress/singer Kassie DePaiva on the TV show "The View" had catapulted her to the No. 1 slot on the Hot Topics list, with 6 percent of the queries coming from New York.
Users can also check the top 100 "Hot Trends" for each day, going back to May 15.
Google Trends is under the Google Labs listings, and is still in an early stage of development. Google warns, "The data Google Trends produces may contain inaccuracies for a number of reasons, including data-sampling issues and a variety of approximations that Trends makes use of. We hope you find this service interesting and entertaining, but you probably don't want to write your PhD dissertation based on this information."
For more information, visit the Google Trends website.