Debian is a popular Linux distribution, that's used primarily on desktop computers, however lots of people have begun using it lately as a web server Operating System as well, due to the stability and security it supplies. The latter is a consequence of the fact that Debian is developed and supported by thousands of qualified volunteers internationally, so that any patch that's required to fix some issue is released in a few days. The very same community can also help you with any question or issue which a user may ever encounter, as they can be contacted through email using mailing lists and a qualified response will be sent in around 15-20 minutes. The advantage here is that all of your questions will be addressed by the same people who have developed the Operating System itself and they have an in-depth knowledge of how it works. As Debian is absolutely free, you won't have 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 which are available for it.