Debian is an OS which uses the Linux kernel. Although it is usually set up on desktops, it is being used on more and more web servers too. The reason is that it is very stable, so a server running it will not have to be restarted for months. Debian is also regarded as being one of the most protected Operating Systems available, due to the fact that security patches are released within days after a problem is found. This is possible since thousands of skilled developers are employed by the Debian project on a voluntary basis and not only do they work on the OS itself, they also provide 24/7 support through special e-mail lists and respond within 20 min to any question. Thus, you will enjoy top-notch support directly from the developers who know their own platform in depth, and not from a third-party support team. Debian is also one of several Linux distributions with the highest number of packages - over 30,000. As the Operating System costs nothing to use, you are able to modify both the core as well as any of the packages in the way you see fit. Furthermore, you will not need to pay any license fees.