From their site:
Every hour, 10x10 scans the RSS feeds of several leading international news sources, and performs an elaborate process of weighted linguistic analysis on the text contained in their top news stories. After this process, conclusions are automatically drawn about the hour's most important words. The top 100 words are chosen, along with 100 corresponding images, culled from the source news stories. At the end of each day, month, and year, 10x10 looks back through its archives to conclude the top 100 words for the given time period. In this way, a constantly evolving record of our world is formed, based on prominent world events, without any human input.
The site is amazing and I've been hooked on trying to use it to keep up on top news stories. Pictures are definitely worth a thousand words.