Debian is an OS which uses the Linux kernel. Even though it is usually set up on personal computers, it is being used on a growing number of web servers too. The reason is that it is really stable, so a server running it will not need to be restarted for months. Debian is also considered to be one of the most protected Operating Systems nowadays, since security patches are released within days after an issue is discovered. This is possible since 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 through special mailing lists and reply in 20 minutes to any question. Thus, you'll obtain 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 one of several Linux releases with the highest number of packages - more than 30,000. Since the Operating System is completely free to use, you will be able to modify both the core and any of the packages in the way you see fit. Also, you won't have to pay any kind of license fees.