Google Caffeine is a new search architecture to return search results faster and to better deal with real-time updated information from social media services including Facebook and Twitter.
Google’s engineers want to refine Google’s next generation search infrastructure which will lead to faster indexing speed, more accurate and comprehensive organic search results, and the inclusion of new dimensions that are not currently showing up in Google web search results. To develop the next generation search engine, Google has opened up a preview of Google’s new Caffeine update. You can help Google test the new Caffeine update search results:
Google requires you to look for differences between the search results within the Caffeine preview and those within the traditional Google web search (e.g. www.Google.com).
To give feedback to Google (according to Matt Cutts):
If you want to give us feedback on how the search results are different, look on the search results page for a link at the bottom of the page that says “Dissatisfied? Help us improve.” Click on that link and type your feedback in the text box. Make sure to include the word caffeine somewhere in the feedback.
Matt Cutts explained Google Caffeine in this video.