Threat and Advantage clarification

[Dr. Jay 1]

I have recently gotten the beginner set and begun reading through the encounters/rules. I will be a first time DM when we play, so I wanted to get some clarification of the rules concerning threat and advantage. As I initiallly understood it, what happened with threat and advantage was determined by the GM. So, if you rolled a success, but with threat, you might shoot your target, but your gun jams. While if you failed with advantage, you might miss your target but, for instance, he has to duck to avoid fire and gets a setback die next round or something. Either way, it seemed like the GM determined what happens. Also, as I read through all the examples given on the product pages for EotE, it seemed this way as well. However, in the encounter book, it says that if advantage is left after the roll, the player gets to determine what happens with it, like using it to take an extra maneuver. Can someone tell me how this is supposed to be played?  Thanks!

[Mark It Zero 50]

Early on it's up to the GM to help adjudicate these. Probably because it's expected that he will be the most capable. Once we are used to the game, I fully intend to empower my players to suggest uses for Advantage, and maybe even Threat if the ideas are entertaining enough.

Now, I go prep the space for my first game!