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 1,079,233 websites that are WordPress Stats Customers. We know of 55,624 live websites using WordPress Stats and an additional 1,023,609 sites that used WordPress Stats historically and 35,931 websites in the United States.
Get a list of 1,079,233 websites using WordPress Stats which includes location information, hosting data, contact details, 55,624 currently live websites and an additional 23,578 domains that redirect to sites in this list. 1,023,609 sites that used this technology previously and 35,931 websites in the United States currently using WordPress Stats.