Debian is an OS which uses the Linux kernel. Although it is usually installed on desktop machines, it's being used on more and more web servers as well. The reason is that it's really stable, so a server running it won't need to be restarted for months. Debian is also regarded as being among the most secure Operating Systems out there, since security patches are released within days after an issue is found. This is possible because thousands of well-experienced developers are part of the Debian project on a voluntary basis and not only do they work on the OS itself, but they also provide 24/7 support via special e-mail lists and reply within twenty minutes to any kind of question. In this light, you will have an outstanding level of 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 releases with the highest number of packages - over 30,000. Since the Operating System is free to use, you are able to modify both the core as well as all of the packages in the way you see fit. Also, you will not have to pay any kind of license fees.