A feedback loop is a closed chain of causal connections from a stock, through a set of decisions or rules or physical laws or actions that are dependent on the level of the stock, and back again through a flow to change the stock.
Reinforcing Feedback Loop An amplifying or enhancing feedback loop, also known as a “positive feedback loop” because it reinforces the direction of change. These are vicious cycles and virtuous circles. Reinforcing feedback loops are self-enhancing, leading to exponential growth or to runaway collapses over time.
Balancing Feedback Loop A stabilizing, goal-seeking, regulating feedback loop, also know as a “negative feedback loop” because it opposes, or reverses, whatever direction of change is imposed on the system.
Meadows, Donella H.. Thinking in Systems (p. 189). Chelsea Green Publishing. Kindle Edition.