Debian is an OS which uses the Linux kernel. Although it is usually installed on desktop machines, it's being used on an increasing number of web servers too. The reason is that it's very stable, so a server running it won't need to be restarted for months. Debian is also regarded as being among the most protected Operating Systems to be found, because security patches are released within days after a problem is discovered. This is possible because thousands of 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 through special e-mail lists and reply within twenty minutes to any question. In this light, you'll obtain 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 distributions with the highest number of packages - over 30,000. Since the Operating System is completely free to use, you can modify both the core as well as any of the packages in the way you see fit. Also, you won't need to pay any kind of license fees.