GFF runs in the background and communicates with the browser, using an appropriate operating system mechanism. GFF has no user interface to speak of. In the normal course of events, GFF behaves like this:
During initialization, GFF attempts to contact a running browser. If it fails, GFF starts a browser for you. After contacting a browser, GFF sets up the communication mechanism and recedes into the background. From this point on, you can ignore GFF; it will run silently in the background handling requests from the browser.
When the browser exits, GFF notices this fact and silently exits as well.
You can end GFF explicitly, without closing the browser:
kill -TERM `cat $HOME/.gff.pid`
On some systems, if GFF started the browser, GFF can be configured to end the browser if you exit GFF directly.