Having root-level access to a server signifies that you will be able to view and update any file on it, including important system files. You may also set up software which can modify specific settings on your server throughout the, so the installation can be performed only if you're logged in as the root user. The latter has full privileges, which means that you'll have full control over the machine whenever you want and you'll be able to do anything you need. You may also make additional users either with similar rights or with fewer rights, according to what you require them for - day-to-day tasks, other server administrators, etcetera. To be on the safe side, it's usually recommended to use the root account only when you really need it and not for tasks which can be done through other accounts. You may use a web-based graphical interface or a Secure Shell console to connect to the server and to manage it at the root level.