Debian is an OS which uses the Linux kernel. Though it is usually installed on desktop computers, it is being used on more and more web servers as well. The reason is that it is 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 available, because security patches are released within days after an issue is found. This is possible because thousands of well-trained 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 by using special mailing lists and respond in 20 minutes to any kind of question. In this light, you will get 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 - over 30,000. Since the Operating System is free to use, you are able to modify both the core and any of the packages in the way you see fit. Furthermore, you won't have to pay any kind of license fees.