Debian is an Operating System that uses the Linux kernel. Even though it is usually set up on desktop machines, it's being used on a growing number of web servers too. The reason is that it is very stable, so a server running it will not need to be restarted for months. Debian is also regarded as being one of the most secure Operating Systems nowadays, due to the fact that security patches are released within days after an issue is found. This is possible because thousands of skilled developers are employed by the Debian project on a voluntary basis and not only do they work on the OS itself, in addition, they provide 24/7 support through special mailing lists and reply in 20 minutes to any question. In this light, you will get top-notch support directly from the developers who know their own platform in detail, and not from a third-party support team. Debian is also one of several Linux releases with the highest number of packages - over 30,000. Since the Operating System is absolutely free to use, you are able to modify both the core and all of the packages in the way you see fit. Also, you won't have to pay any kind of license fees.