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 1,106,218 websites that are WordPress Stats Customers. We know of 61,522 live websites using WordPress Stats and an additional 1,044,696 sites that used WordPress Stats historically and 39,573 websites in the United States.
Get a list of 1,106,218 websites using WordPress Stats which includes location information, hosting data, contact details, 74,172 currently live websites which includes 12,650 domains that redirect to sites in the list. 1,044,696 sites that used this technology previously and 39,573 websites in the United States currently using WordPress Stats.