Apache is an open source Web server originally formed by taking all the "patches" (fixes) to the NCSA Web server and making a new server out of it. The name 'Apache' was chosen from respect for the Native American Indian tribe of Apache, well-known for their superior skills in warfare strategy and their inexhaustible endurance.
Apache is primarily used to serve both static content and dynamic Web pages on the World Wide Web. Many web applications are designed expecting the environment and features that apache provides. apache supports a large array of features including add-on module support which extend its functionality. These include languages such as mod_perl and PHP.
Apache is a freely available and distributed under an "open source" license. It runs on UNIX based operating systems (such as Linux, Solaris, Digital UNIX, and AIX), on other UNIX/POSIX-derived systems (such as Rhapsody, BeOS, and BS2000/OSD), on AmigaOS, and on Windows 2000. According to a recent server survey 60% of all Web sites on the Internet are using Apache (62% including Apache derivatives), making Apache more widely used than all other Web servers combined.
We run apache on all of our 64-Bit Enterprise Linux servers.