From Linux.com:

Managing one site on a Web server can be tough enough, and the job is even harder if you have to host multiple client sites on a badly configured setup. If you're running Apache, you can make things easier by setting up virtual hosts, which let you control multiple domains on one IP address, allowing you to specify URLs like http://clientsdomain.com/file_name.html instead of http://yoursite.com/hosted/clients_directory/file_name.html, and letting you forgo setting up domain forwarding with a /srv/www/htdocs/hosted/clients_directory file.

Read the full thing at http://www.linux.com/feature/118471