After Ctrl-Alt-1/2/3 to terminal, how do you get back into Gnome?

[Chanchao]

After you jump to a text terminal screen, how do you get back to where
you were in the graphical environment?  I think Ctrl-Alt-1 WAS the
graphical environment??

Same for when you hit Ctrl-Alt-Backspace, then you suddenly find
yourself in limbo.. How do you then get Gnome back up?  It seems it
keeps certain things running, like the panels, which then fail to start
when you go back in. 

Also it seems that Alt-F2 to run a command is linked to a panel; it
doesn't work if the panel isn't there (or crashed, etc.) so then you're
stuck, is that so?

Is there a key combination that ALWAYS gets you somewhere where you can
sort out the mess, similar to Ctrl-Alt-Delete in Windows which brings up
the task manager?

Cheers,
Chanchao