Debian is an OS that uses the Linux kernel. Though it is usually set up on desktop machines, it is being used on more and more web servers too. The reason is that it is 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 protected Operating Systems in existence, as security patches are released within days after a problem is found. This is possible because thousands of well-experienced developers are employed by the Debian project on a voluntary basis and not only do they work on the OS itself, they also provide 24/7 support through special e-mail lists and respond in twenty minutes to any kind of question. In this light, you'll get an outstanding level of 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 distributions with the highest number of packages - over 30,000. Since the Operating System is completely free to use, you're able to modify both the core as well as all the packages in any way you see fit. Also, you won't be required to pay any kind of license fees.