What is Google Analytics ?
Google Analytics (GA) is a free service offered by Google that generates detailed statistics about the visitors to a website. Its main highlight is that a webmaster can optimize his/her AdWords advertisement and marketing campaigns through the use of GA’s analysis of where the visitors came from, how long they stayed on the website and their geographical position.
Users can define and track conversions, or goals. Goals might include sales, lead generation, viewing a specific page, or downloading a particular file. By using this tool, marketers can determine which ads are performing, and which are not, as well as find unexpected sources of quality visitors.

I have found that using the Google Analytics a great resource , it was easy to install and gave me all the information i could want on site stats. Hightly recommend it.