Having root-level access to a server signifies that you can view and modify any file on it, including crucial system files. You may also install software which can modify specific settings on your server throughout the, so the installation can be performed only if you are logged in as the root user. The latter has full privileges, which means that you will have full control over your machine whenever you want and you'll be able to do anything you would like. You can also generate additional users either with the same rights or with fewer rights, depending on what you need them for - daily tasks, other server admins, etcetera. To be on the safe side, it is usually recommended to use 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 connect with the server and to control it at the root level.