cntrl-alt-F1 ... how to get back?

[Herman Aalderink]

The list of cli-instructions showed:
ctrl-alt-F1 ............ (to get to the cmd-line)

I tried it
(like being parachuted in the middle of the Pacific)
I logged-in OK.
How do I get back !!! (to the GUI where I came from)

I was running Ubuntu GUI and trying to learn something.
Log-in, Log-out works but does not get me back.
No choice but to restart. I found cntl-alt-del was working.

Yes, I know I can use "Terminal/ Use the command-line".
 (from GUI/ Gnome)
I normally do.

Herman in Philippines.