Overview and Project Information about the Apache Foundation Apache HTTPD Web Server
The Apache Project is a collaborative software development effort aimed at creating a robust, commercial-grade, featureful, and freely-available source code implementation of an HTTP (Web) server. The project is jointly managed by a group of volunteers located around the world, using the Internet and the Web to communicate, plan, and develop the server and its related documentation.
The Netcraft survey shows relative share, by type of domain (.com, .net, etc.) for each of the major HTTP servers
Seems like it's important to the ASF (Apache Software Foundation) to distinguish the grandaddy project from the all the various subprojects that have grown up into Apache.
"The Apache HTTP Server Project is an effort to develop and maintain an open-source HTTP server for modern operating systems including UNIX and Windows NT. 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. Apache has been the most popular web server on the Internet since April of 1996. The February 2005 Netcraft Web Server Survey found that more than 68\% of the web sites on the Internet are using Apache, thus making it more widely used than all other web servers combined."
"Apache is the world's most popular HTTP server, being quite possibly the best around in terms of functionality, efficiency, security and speed."