Having root-level access to a 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 update specific settings on the server during the process, so the installation can be performed only if you're signed in as the root user. The aforementioned has full privileges, which means that you will have full control over the machine whenever you want and you'll be able to do anything you would like. You may also create various other users either with the same rights or with fewer rights, depending on what you need them for - daily tasks, other server administrators, etc. To be on the safe side, it's usually recommended to use the root account only when you actually need it and not for tasks you can do through other accounts. You may use a web-based graphical interface or a Secure Shell console in order to connect with the server and to manage it at the root level.