Apache is Unix-based, open-source Web server that is used to host about half the sites on the Internet. Originally, Apache was a Unix product, but now versions for Windows, OS/2 and other platforms exist. As with most open-source projects, there are numerous add-ons and tailored versions of the server available, which are created using the Apache module API. The name comes from its origins as a series of "patch files." Read Webmonkey’s Tuning Apache article for more details about Apache.