Having root-level access to your server signifies that you can view and update any file on it, which includes essential system files. You may also set up software that can change certain settings on the server throughout the, so that the installation can be done only if you're 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 will be able to perform anything you need. You can also generate additional users either with the same rights or with fewer rights, according to what you want them for - everyday tasks, other server administrators, 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 that you can do through other accounts. You may use a web-based graphical interface or a Secure Shell console to connect to the server and to control it at the root level.