Apache is a free and open-source cross-platform web server software.
Google AdSense is a program run by Google through which website publishers serve advertisements that are targeted to the site content and audience.
Mod_dav is an Apache module to provide WebDAV capabilities for your Apache web server. It is an open-source module, provided under an Apache-style license.
PHP is a general-purpose scripting language used for web development.
Unix is a family of multitasking, multiuser computer operating systems.