If you get a server of your own, it will operate independently, so it will have its own Operating System and you could later install server side applications directly or script-driven internet sites via a hosting Control Panel. While keeping the Os updated isn't always considered fundamental, it can be a quite important task for a number of reasons. A more modern OS version may have better support for specific hardware, so you may get better performance for the sites and web applications you install. Your server will also be more protected as updates usually include security patches that take care of small issues that may permit unauthorized individuals to access your content. Last, but not least, newer script versions, which are also released for both improved security and for additional features, might require a later version of the Os in order to work effectively and with their full capabilities.