The Free On-line Dictionary of Computing (18 March 2015):
(Or "web server") A server process running
at a website which sends out web pages in response to
HTTP requests from remote browsers.
If one site runs more than one server they must use different
port numbers. Alternatively, several hostnames may be
mapped to the same computer in which case they are known as
Apache and NCSA HTTPd are two popular web servers.
There are many others including some for practically every
platform. Servers differ mostly in the "server-side"
features they offer such as server-side include, and in
their authentication and access control mechanisms. All
decent servers support CGI and most have some binary API