Debian is a well-known Linux distribution, that's used mainly on PC's, but lots of people have begun using it lately as a web server OS too, because of the stability and protection it provides. The latter is a direct result the fact that Debian is developed and supported by numerous qualified volunteers around the globe, so any patch which is necessary to fix a particular issue is released within a few days. The very 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 e-mail lists and a qualified response will be sent in no more than 15-20 min. The advantage here is that all your questions will be answered by the same people who have developed the Operating System itself and they have a detailed knowledge of how it functions. As Debian is absolutely free, you won't need to pay any license fees to use it and you can personalize it as much as you want or need. This is valid for the Operating System as well as the 30.000+ software packages that are readily available for it.