Debian is an OS which uses the Linux kernel. Although it is usually installed on desktop computers, it is being used on more and more 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 secure Operating Systems to choose from, because security patches are released within days after an issue is discovered. This is possible because thousands of well-trained developers are part of 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 e-mail lists and respond in 20 minutes to any kind of question. Thus, 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 one of several Linux releases with the highest number of packages - over 30,000. As the Operating System is free to use, you are able to modify both the core and all the packages in the way you see fit. Also, you will not be required to pay any license fees.