Having root-level access to your server signifies that you can view and modify any file on it, including essential system files. You can also set up software that can update certain settings on your server during the process, so that the installation can be performed 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 do anything you would like. You can also make other users either with identical rights or with fewer rights, depending on what you need them for - daily tasks, other server admins, etc. To be on the safe side, it's usually recommended to employ the root account only when you actually need it and not for tasks 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.