Google Analytics is a service provided by Google that tracks web statistics.
Some of Google Analytics features include tracking how users found a site by listing referral traffic from search engines, tracking what keywords were searched, how a site was explored, displays what links were clicked on and how long users were on the site. Google.com: What is Google Analytics?
Google Analytics is also integrated with AdWords. AdWords is used to create pay-per-click and targeted advertisements on sites for specific keywords. This feature is most helpful for internet marketing.