Debian is an Operating System that uses the Linux kernel. Though it is usually set up on desktop machines, it is being used on an increasing number of web servers too. The reason is that it is really stable, so a server running it will not have to be restarted for months. Debian is also considered to be one of the most risk-free Operating Systems to choose from, because security patches are released within days after an issue is discovered. This is possible since thousands of skilled developers are part of the Debian project on a voluntary basis and not only do they work on the OS itself, in addition, they provide 24/7 support via special e-mail lists and reply within 20 minutes to any kind of question. Thus, you will get top-level support directly from the developers who know their own platform in depth, and not from a third-party support team. Debian is also among the Linux releases with the highest number of packages - more than 30,000. As the Operating System costs nothing to use, you can modify both the core as well as all the packages in the way you see fit. In addition, you won't need to pay any kind of license fees.