Debian is an OS that uses the Linux kernel. Although it is usually installed on desktops, it's being used on more and more web servers as well. The reason is that it's 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 nowadays, due to the fact that security patches are released within days after a problem is found. This is possible because 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, they also provide 24/7 support by using special mailing lists and reply in 20 minutes to any question. Thus, 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 releases with the highest number of packages - more than 30,000. Since the Operating System is free to use, you are able to modify both the core and any of the packages in the way you see fit. Furthermore, you will not need to pay any license fees.