Debian is an OS which uses the Linux kernel. Though it is usually installed on desktops, it's being used on more and more web servers as well. The reason is that it's very stable, so a server running it will not have to be restarted for months. Debian is also regarded as being one of the most risk-free Operating Systems out there, due to the fact that security patches are released within days after a problem is found. This is possible since thousands of qualified developers are working for 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 respond in twenty minutes to any question. Thus, you'll obtain 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 several Linux releases with the highest number of packages - over 30,000. As the Operating System is absolutely free to use, you will be able to modify both the core as well as any of the packages in the way you see fit. Also, you won't be required to pay any kind of license fees.