According to Wikipédia (lien):
"Google Analytics is a freemium web analytics service offered by Google that tracks and reports website traffic. Google launched the service in November 2005 after acquiring Urchin. Google Analytics is now the most widely used web analytics service on the Internet."
Here is the official page of Google Analytics
On Xotelia, you can enter your Google Analytics ID in order to get report on Analytics f what happens on the booking engine.