The rules mention something called ‘the ambient’. What is this exactly? I couldn’t find it explained anywhere.
I think you are talking about the "actions" in the chapter "run and gun" right? It's an example of using the sorroundings described bybthe referee as advantage. If the referee for example describes a scenery where there's ruins around the combat zone, you can try to make some decaying ruins fall onto your enemy, that's using the ambient to fight for you.