Debian is an Operating System which uses the Linux kernel. Although it is usually installed on desktops, 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 one of the most protected Operating Systems nowadays, due to the fact that security patches are released within days after a problem is found. This is possible since thousands of qualified 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 by using special e-mail lists and reply 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 depth, and not from a third-party support team. Debian is also one of several Linux distributions with the highest number of packages - over 30,000. As the Operating System is completely free to use, you'll be able to modify both the core and all the packages in any way you see fit. Furthermore, you will not be required to pay any license fees.