The Open Learning Centre

The Apache Web Server from the Apache Software Foundation. It's a legendary product in many ways. The Internet as we know it now almost certainly wouldn't be here if it wasn't for Apache's web server.

It is currently, and has been for many years, the number one web server on the Internet according to most analytical reports. This is despite the extreme lengths that some rivals have gone to to try and skew the figures. The widely read monthly survey by Netcraft shows that in July 2008, Apache was serving almost 50% of the worlds web sites. Apache has been the most popular web server on the Internet since April 1996.

The Apache web server became so popular for several reasons:

• Cost: It is Open Source and free
• Cross Platform: Apache runs on almost every mainstream Operating System
• Modular: Plugin modules enable wide support for building interactive and dynamic web sites using a multitude of backend services. Highly popular is the combination of the MySQL database and the PHP programming language.
• Performance: Consistently Apache has outperformed its rivals in terms of raw page impression performance, efficiency of memory and processor cycle usage and its ability to scale to support many websites within one running server instance.
  

There is a good description of the history of Apache here on the Wikipedia.

Needless to say, the site you are reading this on, is being served by Apache. It is also using the MySQL database and the Joomla! Content Management System (written in PHP).