Debian is an OS that uses the Linux kernel. Although it is usually set up on desktop machines, it's being used on an increasing number of web servers too. The reason is that it's very stable, so a server running it won't need to be restarted for months. Debian is also regarded as being one of the most risk-free Operating Systems you can get, because security patches are released within days after an issue is discovered. This is possible because thousands of experienced developers work 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 mailing lists and reply within twenty minutes to any question. Thus, you'll get 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 among the Linux distributions with the highest number of packages - over 30,000. Since the Operating System is completely free to use, you can modify both the core and all the packages in any way you see fit. In addition, you won't have to pay any license fees.