Debian is an Operating System which uses the Linux kernel. Although it is usually installed on desktops, it is being used on an increasing number of web servers too. The reason is that it is really stable, so a server running it won't need to be restarted for months. Debian is also regarded as being one of the most secure Operating Systems you can get, as security patches are released within days after a problem is discovered. This is possible because thousands of experienced developers are working for the Debian project on a voluntary basis and not only do they work on the OS itself, but they also provide 24/7 support via special e-mail lists and respond within twenty minutes to any kind of question. In this light, you'll have 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 releases with the highest number of packages - more than 30,000. As the Operating System costs nothing to use, you're able to modify both the core as well as all of the packages in any way you see fit. In addition, you won't be required to pay any kind of license fees.