Positive and Negative Feedback

Noise is related to lots of ants bumping into each other. It's almost like a disturbance. An ant is following a past and it bumps into another ant that has some pheromone which means the first ant will leave its original past and do something different. The consequence of that is not clear. It can be positive or negative. But when many of these somewhat random encounters leading to somewhat random decisions are being taken, if the system is large enough on the whole, the system will actually find a good solution to its problem. That's probably what we mean by noise and complex systems.