Debian is an Operating System which uses the Linux kernel. Though it is usually set up on personal computers, it is being used on a growing number of web servers too. The reason is that it is very stable, so a server running it will not have to be restarted for months. Debian is also considered to be one of the most risk-free Operating Systems out there, as security patches are released within days after a problem is discovered. This is possible because thousands of skilled 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 by using special e-mail lists and respond in 20 min to any question. In this light, you'll receive 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 the Linux releases with the highest number of packages - more than 30,000. Since the Operating System is free to use, you will be able to modify both the core as well as any of the packages in any way you see fit. Also, you will not need to pay any kind of license fees.