It basically lets you see the history of a search term’s use over time… and if the search term appears in Google News as well, you see that along with regular web searches. Just as with Google Finance, there are links along the chart to news items that occurred at that point in time. A search for ‘tivo’ yields:
You can also view the popularity of a search term by city, region, and language.
Even cooler is that you can supply multiple search terms and compare them all on the same chart. This lets you do things similar to what the “Google Fight” site has done for a while (by running both searches and scraping the count of items found). Here’s a comparison between the phrases “playstation 3” and “xbox 360”:
I’m not sure how current these search results are, but with E3 happening this week and a bunch of PS3 announcements, I’d expect to see a spike there pretty quick (for both, though probably with PS3 searches surpassing 360 searches for a time).
Also interesting with this search is how Seattle appears in the searches-by-city result… among the lowest in searches for “Playstation 3” and the highest of all with searches for “xbox 360”. Wonder why.