Piwik is an open source web analytics application. This is the software that we use to track visits to your websites.
We prefer Piwik over Google Analytics, because you own the data that Piwik generates. With Google Analytics, you do not own any of the data that is generated, and Google has the right (enshrined in its terms and conditions) to use it in ways you or your visitors may not agree with.
Piwik is robust and in constant development. It generates a lot of useful data (which can be configured to your needs). For more information, please visit our Piwik manual.