Debian is a widespread Linux distribution, that is used primarily on desktop machines, but numerous people have started using it lately as a web server Operating System too, due to the stability and security it offers. The latter is a result of the fact that Debian is developed and supported by thousands of qualified volunteers all around the world, so any patch that is necessary to fix a certain issue is released within a few days. The very same community can also help you with any question or trouble that a user may ever have, due to the fact that they can be contacted via e-mail using mailing lists and a qualified response will be sent in no more than 15-20 minutes. The advantage here is that your queries will be answered by the same people who have designed 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 license fees to use it and you can customize it as much as you want or need. This is valid for the Operating System and the 30.000+ software packages which are available for it.