Virtual Web servers are a very popular way of providing low-cost web hosting services. Instead of requiring a separate computer for each server, dozens of virtual servers can co-reside on the same computer. In most cases, performance is not affected and each web site behaves as if it is being served by a dedicated server. However, if too many virtual servers reside on the same computer, or if one virtual server starts hogging resources, Web pages will be delivered more slowly.

Also see the Server Types page in the Quick Reference section of Webopedia for a comparison of server types.

The Truth About Servers
What makes a server a server? Is there a difference between an e-mail server and a messaging server? Should a firewall be considered a server in certain circumstances? These questions and more are answered in an extensive tutorial that cuts through the marketing hype and explains the basics of key server types.