Debian is a widespread Linux distribution, which is used mainly on desktop machines, still a lot of people have begun using it lately as a web server OS too, due to the stability and security it provides. The latter is a direct result the fact that Debian is developed and supported by a large number of qualified volunteers around the globe, so that any patch that's necessary to fix a certain issue is released within a matter of days. The very same community will also help with any question or trouble that a user may ever have, as they can be contacted through electronic mail using mailing lists and a competent response will be sent in around 15-20 minutes. The advantage here is that all of your questions will be replied by the same people who have designed the Operating System itself and they have an in-depth knowledge of how it works. As Debian is provided for free, you will not 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 both the Operating System and the 30.000+ software packages which are readily available for it.