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 1,097,383 websites that are WordPress Stats Customers. We know of 62,733 live websites using WordPress Stats and an additional 1,034,650 sites that used WordPress Stats historically and 40,063 websites in the United States.
Get a list of 1,097,383 websites using WordPress Stats which includes location information, hosting data, contact details, 87,246 currently live websites which includes 24,513 domains that redirect to sites in the list. 1,034,650 sites that used this technology previously and 40,063 websites in the United States currently using WordPress Stats.