Gmod command.. need help here

I was playing a perp server once where an admin had a screenshot of his screen.
He had a sort of "console" ingame without really opening the big console.
It's like an overlay, I can't seem to find the command and I am sure it does exist.
It's like a yellow/orange text in your top left screen, anyone know what I mean?

you probably mean the convar 'developer' which shows the console at top left
it's absolutely useless though.