Debian is an OS that uses the Linux kernel. Although it is usually set up on personal computers, it's being used on more and more web servers too. The reason is that it's really stable, so a server running it won't have to be restarted for months. Debian is also regarded as being among the most safe Operating Systems in existence, due to the fact that security patches are released within days after an issue is found. This is possible because thousands of well-experienced developers are working for 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 mailing lists and respond in twenty minutes to any question. In this light, you will have 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 the Linux distributions with the highest number of packages - over 30,000. Since the Operating System is completely free to use, you are able to modify both the core as well as all the packages in the way you see fit. Furthermore, you won't need to pay any kind of license fees.