Debian is an OS which uses the Linux kernel. Though it is usually set up on desktop computers, it's being used on more and more web servers too. 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 one of the most risk-free Operating Systems to choose from, due to the fact that security patches are released within days after an issue is found. 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, they also provide 24/7 support by using special mailing lists and reply in 20 minutes to any kind of question. In this light, you will have top-notch 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 distributions with the highest number of packages - more than 30,000. As the Operating System is completely free to use, you will be able to modify both the core and any of the packages in any way you see fit. Furthermore, you won't be required to pay any license fees.