Web statistic software tracks the interaction of visitors with your website. While "hits" (requests for a single item from a web server, including images, style sheets, script files and others as well as pages themselves) or "page views" (entire page views) provide an indication of how many visitors there are to a site, much more useful information can be tracked.
You can track entry or exit statistics (where in your site users enter/exit), referrer statistics (where most of your traffic is coming from) and more information about your visitors such as browser and connection statistics.
All this information can be invaluable in producing a targeted and relevant presence online. Such statistics are also key in making decisions as to content or redesign strategies.
Third party companies are generally used to collate and summarise these statistics into something meaningful. The WMS places no restriction on which third party is chosen, most times it is a case of adding the correct code to all website page templates. One of the best web statistics packages we have found is Google Analytics.