Debian is an OS which uses the Linux kernel. Though it is usually installed on desktops, it is being used on an increasing number of web servers as well. The reason is that it is really stable, so a server running it won't have to be restarted for months. Debian is also considered to be among the most protected Operating Systems available, because security patches are released within days after an issue is discovered. This is possible since 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, they also provide 24/7 support through special mailing lists and respond within twenty minutes to any question. Thus, you will get an outstanding level of 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 releases with the highest number of packages - more than 30,000. Since the Operating System is absolutely free to use, you'll be able to modify both the core and all the packages in the way you see fit. Also, you won't have to pay any license fees.