Apache is the world's most popular HTTP server, being quite possibly the best around in terms of functionality, efficiency, security and speed.
Apache is one of the most popular web servers on the Internet. Developed by a team of programmers working together via the Internet, with the source code scrutinized by hundreds of others, Apache has developed a reputation for robustness and speed that is unparalleled. More information on Apache can be found on the APACHE website.
Apache is probably the world's most popular open-source web server. An extremely powerful, robust and stable HTTP server with CGI, SSL, and other more advanced features available through optional add-in modules.