A virtual server is a virtual web server that uses a unique combination of IP address, port number, and host name to identify it. You might have several virtual servers all of which use the same IP address and port number but are distinguished by their unique host names.
When you first install Web Server, a default virtual server is created. You can also assign a default virtual server to each new HTTP listener you create. For details, see Sun Java System Web Server 7.0 Update 4 Administrator’s Guide.