Having root-level access to your server signifies that you will be able to view and update any file on it, including important system files. You can also set up software which can change certain settings on the server throughout the, so the installation can be done only if you are signed in as the root user. The aforementioned has full privileges, which means that you'll have full control over the machine whenever you want and you will be able to do anything you want. You can also create various other users either with the same rights or with fewer rights, based on what you need them for - day-to-day tasks, other server admins, etc. To be on the safe side, it's generally recommended to employ the root account only when you really need it and not for tasks that you can do 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 control it at the root level.