Web statistics and analisis gives you an opportunity to track your visitors path over your site, shows which pages are popular and wich are not, track keywords and search engines that bring you visitors. Lots of useful information like banwidth usage, unique visitors, hits, visiy length, countries and languages of your visitors.
Free tools provided by every hosting company are Webalizer and AWStat, which are quite inaccurate and do not give overall information. We recommend free statcounter.com . Also there are hundreds of commercial solutions we do not want to advertise, but the majotity of them really worth buying. These analitics tools usually provide full and overall information on you visitors and give useful advuces. Hey! Almost forgot about Google Analitics, it also rulez!