Debian is a popular Linux distribution, that is used mainly on desktop machines, but many people have begun using it lately as a web server Operating System as well, due to the stability and security it offers. The latter is a result of the fact that Debian is developed and supported by numerous qualified volunteers around the globe, so any patch that's required to fix some issue is released in a few days. The same community will also help with any question or issue that a user may ever experience, since they can be contacted via electronic mail using mailing lists and a competent response will be sent in no more than 15-20 minutes. The advantage here is that all your questions will be responded to by the same people who have created the Operating System itself and they have an in-depth knowledge of how it functions. As Debian is free, you will not need to pay any kind of license fees to use it and you can customize it as much as you want or need. This is valid for both the Operating System as well as the 30.000+ software packages that are readily available for it.