Debian is a well-known Linux release, that's used primarily on PC's, still lots of people have started using it lately as a web server OS too, because of the stability and protection it provides. The latter is a consequence of the fact that Debian is developed and supported by countless qualified volunteers all around the world, therefore any patch which is necessary to fix some issue is released in a matter of days. The very same community can also help you with any question or trouble that a user may ever have, as they can be contacted via e-mail using e-mail lists and a qualified response will be sent in no more than 15-20 minutes. The advantage here is that your questions will be responded to by the same people who have designed the Operating System itself and they have a detailed knowledge of how it works. As Debian is provided for free, you won't have to pay any kind of license fees to use it and you'll be able to customize 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 available for it.