Apache is the most widely used
HTTP server on the
internet. It is a powerful and flexible server, and supports the most recent Internet protocols including
HTTP/1.1. It has a modular design that allows it to be customized to support things like
Java servlets and
PHP.
Apache started life as patches to the NCSA httpd web server informally shared by webmasters. In April 1995, the first full Apache server was released, and the rest, as they say, is history. The name Apache comes from these humble beginnings ("a patchy" server).
Apache is an open source project, meaning all the source code is available to the public. The license is similar to the BSD license, in that there are no restrictions against using Apache in a commercial, closed source, project.
The server runs on most operating systems, including Windows NT/2000, Windows 9x, OS/2, MacOS X, and most Unix variants. Apache has been coded with correctness and flexibility as goals rather than speed, so Apache is rarely the fastest web server for a platform, but it is rock solid and generally useful for the vast majority of situations.
Some of the most popular features of Apache are:
- highly scalable DBM databases for authentication information.
- content negotiation for supporting multiple versions of HTML and levels of standards compliance.
- virtual hosting, or allowing one Apache server to serve content for multiple ip addresses or domain names.
Sources: Apache FAQ