Google Analytics tells you everything you want to know about how your visitors found you and how they interact with your site. Focus your marketing resources on campaigns and initiatives that deliver ROI, and improve your site to convert more visitors.
Google Analytics has the enterprise level capabilities you'd expect from a high end web analytics offering and also provides timesaving integration with AdWords. Of course, Google Analytic tracks all of your non-AdWords initiatives as well.
In the next few posts I will try and run through how easy it is to set this up, and how to use the info this tool gives you.