Having root-level access to a server means that you will be able to view and modify any file on it, including essential system files. You can also set up software which can change 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, which means that you will have full control over the machine whenever you want and you will be able to do anything you want. You can also make other users either with similar rights or with fewer rights, depending on what you require them for - day-to-day tasks, other server admins, etc. To be on the safe side, it is generally recommended to employ the root account only when you really need it and not for tasks which can be done using 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 manage it at the root level.