Debian is a popular Linux release, that is used primarily on desktop computers, however a lot of people have begun using it lately as a web server OS too, due to the stability and security it provides. The latter is a result of the fact that Debian is developed and supported by numerous qualified volunteers worldwide, so any patch which is necessary to fix a certain issue is released in a matter of days. The very same community will also help you with any question or problem that a user may ever have, as they can be contacted through e-mail using e-mail lists and a qualified response will be sent in no more than 15-20 min. The advantage here is that all of your questions will be responded to by the same people who have created the Operating System itself and they have an in-depth knowledge of how it functions. As Debian is absolutely free, you won't have to pay any kind of license fees to use it and you can personalize 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.