Virtual HostA virtual host
Virtual Hosteling - What is Virtual Hosteling? - The Definition of WhatIs.com
Virtual hosted on the web is the delivery of web host servers hosted on the web, so a business (or individual) does not need to buy and manage its own web servers and connectivity to the web. Sometimes a virtual host is referred to as a web or web "space vendor. A number of organizations that offer this type of support call it "hosting".
Virtual hosted service usually provides a client who wants a Web site with: support for registering domains, several domains associated with the name of the Web site owner, mapping of repositories and directories for Web site content such as HTML and graphics data, email address, and optional Web site building capabilities.
If a client actually wants to have their own servers, some ISPs allow the client to lease a separate site to host the servers. Collocation means that a client is permitted to place his own bought devices at the provider's site.
Virtual Host means the practical operation of more than one website (e.g. company1.example.com and company2.example.com) on a common one. The virtual host can be "IP-based," which means you have a different IP for each site, or "name-based," which means you have more than one name on each IP.
Sometimes the last variation of virtual host is referred to as host-based or non-IP-enabled virtual host. When you try to debug your virtual host config, you may find the -S switches useful.