Trends are a new way to look at the searches you've done on Google. To
use Trends, you need to have Personalized Search turned on and be
signed in to your Google Account. You'll see graphs and lists detailing
your own search activity, including top searches, most-visited
websites, daily activity by hour and other interesting tidbits. If no
Trends appear, just check back in a couple of days.
http://www.google.com/psearch/trends