Simple CMS' can be used for running full blown portal to simple news site...
being able to manage the sites content automatically without having to run the content through HTML editing software and upload it. Instead you can just fill in a form on a site and click send and a news article is created magically...
Links and Downloads Databases are also part of a good CMS as well as Forums and the likes...
check out
Web-APP.net for a great FREE CMS and get WebAPPing your site today!!!!
You can modify scripts like this for full blown portals or simple CMS based websites which are easy to maintain and add content to without ftping in or HTMLing up content!!!