Debian is a Linux distribution, which is preffered for desktop machines, but it's been becoming more popular as a server OS over the last few years as well. It is very dependable and safe, as fixes are released within a couple of days after a problem is discovered. Debian has a large support community, so when you have any questions or troubles with the OS or with some of the 30,000+ packages it is equipped with, you can contact the developers straight away through e-mail using special mailing lists and receive a reply in just 15-20 min. The Debian community offers the best level of support possible, as your questions will be handled by exactly the same people who built Debian in the first place, so they have an in-depth knowledge of how their own system functions. As the Operating System is free to use and distribute, no license charges will be added to your website hosting fees and you'll be able to modify the program code files and any other software which you install without restrictions, in order to optimize the software environment for your websites. In addition, Debian performs very well on any hardware, as it's light and quick and does not need much memory.