If you get a server of your own, it will work independently, so it will have its own Os and you can later install server side programs directly or script-driven websites through a hosting Control Panel. Although keeping the Os updated isn't always considered fundamental, it can be a quite important task for several reasons. A more modern OS version might have better support for specific hardware, so you may get better performance for the internet sites and web apps you install. Your server shall also be more secure since updates typically include security patches that resolve small issues which may allow unauthorized people to access your content. Last, but not least, current script versions, which are also released for both boosted security and for additional features, may require a later version of the Os in order to work effectively and with their 100 % capabilities.