Debian is an OS that uses the Linux kernel. Even though it is usually set up on personal computers, it's being used on a growing number of web servers as well. The reason is that it is really stable, so a server running it will not have to be restarted for months. Debian is also considered to be one of the most safe Operating Systems out there, due to the fact that security patches are released within days after a problem is found. 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, in addition, they provide 24/7 support via special mailing lists and respond in 20 min to any kind of question. In this light, you'll obtain 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. Since the Operating System is completely free to use, you'll be able to modify both the core as well as all of the packages in the way you see fit. Furthermore, you will not be required to pay any kind of license fees.