from the website:
Google Analytics tells you everything you want to know about how your visitors found you and how they interact with your site. You’ll be able to focus your marketing resources on campaigns and initiatives that deliver ROI, and improve your site to convert more visitors.
Learn how visitors interact with your website and identify the navigational bottlenecks that keep them from completing your conversion goals. Find out how profitable your keywords are across search engines and campaigns. Pinpoint where your best customers come from and which markets are most profitable to you. Google Analytics gives you this and more through easy-to-understand visually enhanced reports.