Having root-level access to a server means that you will be able to view and modify any file on it, including crucial system files. You may also set up software that can change particular settings on your server during the process, so that the installation is possible only if you are logged in as the root user. The latter has full privileges, which means that you will have full control over the machine whenever you want and you can do anything you want. You can also generate additional users either with identical rights or with fewer rights, according to what you want them for - day-to-day tasks, other server admins, etc. 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 you can do through other accounts. You may use a web-based graphical interface or a Secure Shell console in order to connect with the server and to control it at the root level.