It is a computer program that serves requested HTML pages or files from the Web client. Every Web server that is connected to the Internet is associated with a unique address, I.e. IP address.
Web server software generally required a fairly robust operating system like Unix, Windows NT. Every Website need to be stored on a computer called the Web server from which it is a can be accessed.
Currently, there are five major Web servers commonly used for hosting website as follow:
Apache HTTP Server
It was developed by Apache software Foundation. The Apache HTTP server is the most popular Web hosting server in the world. This software can be installed Virtually on all operating systems including Windows, Linux Mac OS X, Unix etc. At present, 60% of server machines run on the Apache Web server.
Internet Information Server (IIS)
It is a product of Microsoft and is considered to be a very high performance Web hosting service. It is easily administrable and integrated with the Windows platforms.