This new feature lets you search for website details instead of a keyword detail. The sample graph below shows traffic details for Facebook.com, MySpace.com and Orkut.com.

As you can see in the graph above, Facebook.com has hit 30 Million mark where as MySpace.com is seeing a steady drop, where as Orkut.com shows no data because Google has limited its search functionality for non-Google websites.

Comparing Google Trends for Websites data with other sites offering similar information such as Alexa, Compete, etc.. wont be a good idea because the criteria based on which they show information differs greatly from one another.

Google Trends help page sheds some light on how this information is being collected and shared.

"Trends for Websites combines information from a variety of sources, such as aggregated Google search data, aggregated opt-in anonymous Google Analytics data, opt-in consumer panel data, and other third-party market research. The data is aggregated over millions of users, powered by computer algorithms, and doesn’t contain personally identifiable information." click here to read more from the help page.