Apache is an open-source web server that is widely used due to its features, performance, and availability for free. The document provides instructions on how to install, configure, customize, and uninstall Apache on a Linux system. It describes downloading and extracting the Apache files, running the configuration script, editing the configuration file, starting the server, and testing it in a web browser. It also lists some common Apache modules and provides steps to stop and uninstall Apache if it is no longer needed.