Having root-level access to a server means that you'll be able to view and update any file on it, which includes important system files. You may also set up software which can change certain settings on your server during the process, so that the installation can be performed only if you are logged in as the root user. The aforementioned has full privileges, i.e. you will have full control over your machine whenever you want and you'll be able to do anything you want. You can also make other users either with the same rights or with fewer rights, according to what you want them for - day-to-day tasks, other server admins, etcetera. 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 that can be done through other accounts. You can use a web-based graphical interface or a Secure Shell console in order to connect to the server and to manage it at the root level.