If you get a server of your own, it will run independently, so it will have its own Operating System and you could later install server side applications directly or script-driven websites via a hosting Control Panel. While keeping the Os updated is not always considered fundamental, it can be a quite important task for a variety of reasons. A more modern OS version could have better support for certain hardware, so you could get better performance for the sites and web applications which you install. Your server shall also be more protected since updates typically include security patches that resolve small problems that may enable unauthorized people to access your content. Last, but not least, more modern script versions, which are also released for both increased security and for additional features, might require a later version of the Operating System in order to work effectively and with their full capabilities.