The Apache HTTP Server Project is an effort to develop and maintain an OpenSource HTTP server for modern OperatingSystems including UNIX and WindowsNT. The goal of this project is to provide a secure, efficient and extensible server that provides HTTP services in sync with the current HTTP standards.
It runs on most OpenSource (and not so open source) OperatingSystems. It started life as a heap of patches for NCSA's at the time no longer maintained httpd, circulating among SysAdmins. Eventually, a group of developers collected all the patches and consolidated them into their own version of the web server. Hence the name, a play on words on “A Patchy Server.”