Debian is an Operating System which uses the Linux kernel. Though it is usually installed on desktop computers, it's being used on more and more web servers too. The reason is that it is very stable, so a server running it won't need to be restarted for months. Debian is also considered to be among the most safe Operating Systems available, due to the fact that security patches are released within days after a problem is discovered. This is possible because thousands of experienced developers work 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 by using special mailing lists and respond within 20 minutes to any kind of question. In this light, you will have an outstanding level of support directly from the developers who know their own platform in detail, and not from a third-party support team. Debian is also among the Linux distributions with the highest number of packages - more than 30,000. Since the Operating System costs nothing to use, you will be able to modify both the core and any of the packages in the way you see fit. Furthermore, you won't have to pay any kind of license fees.