Curious about the traffic that is coming to your site? Well then Web Aalytics programs like Google Analytics are great for providing a valuable source of insight on this. You can use such programs to:
get an insight into how users reach and behave on your site;
see what is the most popular content on your site
measure the impact of optimisations you make to your site, for exampe did changing the title and description meta tags improve traffic from search engines?
Advanced user review this information and combine it with data from your server log files to provide even more comprehensive information about how visitors to your site are interacting with documents (such as other key words).
Google and other providers also offer Website Optimiser tools. These programs allow you to run experiments to find what on page changes will produce the best converson rates with visitors. This requires a combination of Google Analystics and Google Webmaster Tools.