Debian is a well-known Linux distribution, that's used primarily on desktop machines, still a lot of people have begun using it lately as a web server Operating System too, due to the stability and protection it offers. The latter is a consequence of the fact that Debian is developed and supported by thousands of qualified volunteers worldwide, so that any patch that's required to fix a certain issue is released in a couple of days. The very same community can also help you with any question or issue that a user may ever have, since they can be contacted via email using mailing lists and a competent response will be sent in around 15-20 min. The advantage here is that your questions will be replied by the same people who have made the Operating System itself and they have a detailed knowledge of how it functions. As Debian is free, you won't need to pay any kind of license fees to use it and you will be able to personalize it as much as you want or need. This is valid for both the Operating System and the 30.000+ software packages which are readily available for it.