Debian is an Operating System that uses the Linux kernel. Although it is usually set up on desktop machines, it is being used on a growing number of web servers too. The reason is that it's really stable, so a server running it won't have to be restarted for months. Debian is also considered to be among the most secure Operating Systems available, since security patches are released within days after a problem is found. This is possible because thousands of qualified developers are employed by the Debian project on a voluntary basis and not only do they work on the OS itself, in addition, they provide 24/7 support via special mailing lists and reply within 20 minutes to any kind of question. In this light, you'll get 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. Since the Operating System is absolutely free to use, you can modify both the core and any of the packages in any way you see fit. Also, you will not need to pay any license fees.