Debian is an Operating System which uses the Linux kernel. Though it is usually set up on personal computers, it's being used on a growing number of web servers too. The reason is that it's really stable, so a server running it won't have to be restarted for months. Debian is also considered to be among the most safe Operating Systems in existence, because security patches are released within days after an issue is discovered. This is possible since thousands of well-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 mailing lists and respond within twenty minutes to any question. Thus, you will have an outstanding level of 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 the Linux distributions with the highest number of packages - over 30,000. Since the Operating System is completely free to use, you can modify both the core and any of the packages in the way you see fit. In addition, you will not be required to pay any kind of license fees.