Having root-level access to a server signifies that you will be able to view and change any file on it, which includes crucial system files. You can also set up software which can change certain settings on the server during the process, so that the installation can be performed only if you are logged in as the root user. The latter has full privileges, i.e. you'll have full control over your machine whenever you want and you will be able to do anything you would like. You may also generate various other users either with similar rights or with fewer rights, according to what you require them for - everyday tasks, other server admins, etcetera. To be on the safe side, it is generally recommended to use the root account only when you really need it and not for tasks which can be done through other accounts. You can use a web-based graphical interface or a Secure Shell console to connect to the server and to manage it at the root level.