Debian is an Operating System which uses the Linux kernel. Even though it is usually set up on desktop computers, it is being used on more and more web servers as well. The reason is that it is really stable, so a server running it won't need to be restarted for months. Debian is also considered to be among the most secure Operating Systems nowadays, because security patches are released within days after an issue is found. 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, but they also provide 24/7 support by using special e-mail lists and respond in 20 minutes to any question. Thus, you'll get 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 is absolutely free to use, you can modify both the core and all the packages in any way you see fit. Also, you won't be required to pay any license fees.