Debian is a popular Linux release, which is used mainly on PC's, however 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 direct result the fact that Debian is developed and supported by numerous qualified volunteers worldwide, therefore any patch that's necessary to fix a certain issue is released in a few days. The same community can also help you with any question or issue that a user may ever have, as they can be contacted via email using e-mail lists and a qualified response will be sent in around 15-20 minutes. The advantage here is that all of your queries will be answered by the same people who have developed the Operating System itself and they have an in-depth knowledge of how it functions. As Debian is absolutely free, you will not have to pay any license fees to use it and you'll be able to customize 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.