The words "negative feedback" give us two important clues about how the system works. The fact that it is a the back system means it's looking backwards at a change that has already occurred. In other words, the controlled variable has moved away from its set point. The fact that this is a negative system means that it is a system that is trying to negate or reverse the change that has already occurred-in other words it is trying to return the controlled variable back to the setpoint.