Tells owners of the website how many people are visiting the site, where they are coming from and whats most interesting to them.
http://wordpress.com/features/stats/
Analytics and Tracking · Audience Measurement · Visitor Count Tracking
Get access to data on 1,057,782 websites that are WordPress Stats Customers. We know of 47,566 live websites using WordPress Stats and an additional 1,010,216 sites that used WordPress Stats historically and 30,858 websites in the United States.
Get a list of 1,057,782 websites using WordPress Stats which includes location information, hosting data, contact details, 47,566 currently live websites and an additional 93,352 domains that redirect to sites in this list. 1,010,216 sites that used this technology previously and 30,858 websites in the United States currently using WordPress Stats.