Debian is a well-known Linux release, that's used primarily on desktop machines, however many people have started using it lately as a web server OS too, because of the stability and protection it supplies. The latter is a direct result the fact that Debian is developed and supported by thousands of qualified volunteers internationally, therefore any patch that is required to fix some issue is released in a couple of days. The same community can also help with any question or problem which a user may ever experience, due to the fact that they can be contacted via electronic mail using e-mail lists and a qualified response will be sent in no more than 15-20 min. The advantage here is that your queries will be replied by the same people who have created the Operating System itself and they have a detailed knowledge of how it works. As Debian is free, you won't have to pay any kind of license fees to use it and you will 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.