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 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 considered to be among the most risk-free Operating Systems out there, due to the fact that security patches are released within days after an issue is discovered. This is possible because thousands of qualified 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 through special mailing lists and respond within twenty minutes to any question. Thus, you will have 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 free to use, you'll be able to modify both the core as well as any of the packages in the way you see fit. In addition, you will not need to pay any kind of license fees.