Debian is an OS which uses the Linux kernel. Even though it is usually installed on desktop computers, it is being used on an increasing number of web servers as well. The reason is that it's very stable, so a server running it won't need to be restarted for months. Debian is also considered to be among the most risk-free Operating Systems to choose from, since 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, they also provide 24/7 support by using special mailing lists and reply in twenty minutes to any kind of question. Thus, you'll obtain top-notch support directly from the developers who know their own platform in depth, 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 costs nothing to use, you can modify both the core as well as all of the packages in the way you see fit. Also, you won't need to pay any kind of license fees.