Having root-level access to your server signifies that you can view and update any file on it, which includes crucial system files. You may also set up software that can modify certain settings on the server throughout the, so that the installation can be done only if you're signed in as the root user. The aforementioned has full privileges, i.e. you'll have full control over the machine whenever you want and you can perform anything you would like. You can also make various other users either with the same rights or with fewer rights, based on what you want them for - everyday tasks, other server admins, etcetera. To be on the safe side, it is usually recommended to employ the root account only when you really need it and not for tasks you can do via other accounts. You can use a web-based graphical interface or a Secure Shell console to be able to connect to the server and to manage it at the root level.