Having root-level access to your server means that you will be able to view and modify any file on it, including crucial system files. You can also install software which can change particular settings on your server throughout the, so that the installation can be performed only if you're logged in as the root user. The aforementioned has full privileges, which means that you will have full control over the machine whenever you want and you will be able to perform anything you would like. You can also generate other users either with similar rights or with fewer rights, based on what you require them for - everyday tasks, other server administrators, etcetera. To be on the safe side, it is generally recommended to use the root account only when you actually 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 be able to connect to the server and to control it at the root level.