Debian is an OS that uses the Linux kernel. Though it is usually installed on desktops, it's being used on a growing number of web servers as well. The reason is that it is very stable, so a server running it won't have to be restarted for months. Debian is also considered to be among the most risk-free Operating Systems you can get, as security patches are released within days after a problem is discovered. This is possible since thousands of experienced 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 by using special mailing lists and reply in 20 minutes to any question. In this light, you will enjoy 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 the Linux releases with the highest number of packages - more than 30,000. As the Operating System costs nothing to use, you'll be able to modify both the core and all of the packages in the way you see fit. Also, you will not have to pay any kind of license fees.