That means you are to login as "root" (for the user name) and for the password you will give "root"'s password. I assume you are the owner of that system and you have the root password (did you install it your self? if yes then you have the password of the root.)
GUI mean Graphic User Interface --that windows and dialogue boxes (usually seen) not the shell or terminal.
Since you are using Fedora you can read and get more answers from this (click here) site