Debian is an Operating System which uses the Linux kernel. Even though it is usually installed on desktops, it's being used on more and more web servers as well. The reason is that it's really stable, so a server running it won't have to be restarted for months. Debian is also regarded as being one of the most secure Operating Systems to choose from, due to the fact that security patches are released within days after an issue is discovered. This is possible since thousands of qualified 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 via special e-mail lists and reply within twenty minutes to any kind of question. Thus, you'll have an outstanding level of 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 - more than 30,000. As the Operating System is completely free to use, you're able to modify both the core and any of the packages in any way you see fit. Furthermore, you will not have to pay any kind of license fees.