Having root-level access to a server means that you will be able to view and change any file on it, which includes crucial system files. You can also set up software which can update specific settings on the server throughout the, so the installation can be performed only if you're logged in as the root user. The aforementioned has full privileges, i.e. you will have full control over the machine whenever you want and you will be able to do anything you need. You can also generate various other users either with identical rights or with fewer rights, depending on what you want them for - everyday tasks, other server admins, etcetera. To be on the safe side, it's generally recommended to employ the root account only when you really need it and not for tasks which can be done via other accounts. You can use a web-based graphical interface or a Secure Shell console to be able to connect with the server and to manage it at the root level.