Debian is an OS which uses the Linux kernel. Though it is usually installed on personal computers, it is being used on an increasing number of web servers as well. The reason is that it is very stable, so a server running it will not need to be restarted for months. Debian is also considered to be one of the most secure Operating Systems nowadays, due to the fact that security patches are released within days after a problem is discovered. This is possible since thousands of well-experienced 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 respond within 20 min to any kind of question. In this light, you'll receive top-level 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 releases with the highest number of packages - more than 30,000. As the Operating System is free to use, you'll be able to modify both the core and all the packages in the way you see fit. Furthermore, you won't be required to pay any kind of license fees.