Debian is an Operating System which uses the Linux kernel. Even though it is usually set up on personal computers, it's 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 regarded as being among the most protected Operating Systems available, because security patches are released within days after a problem is found. This is possible since thousands of experienced developers are working for the Debian project on a voluntary basis and not only do they work on the OS itself, in addition, they provide 24/7 support via special mailing lists and reply within 20 min to any kind of question. Thus, you will obtain 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 absolutely free to use, you are able to modify both the core and all of the packages in the way you see fit. In addition, you will not need to pay any kind of license fees.