Feedback loops are when the output of a function (or system of functions) are fed back in as an input, to modify future outputs. This terminology applies in Control Systems theory, but also in business and other problem-solving areas.
Impressions of how "done" your toast is serves as a feedback loop for adjusting the settings for next time.
A good feedback loop is as short as is feasibly possible while maintaining accuracy, relevance, and authority. Long feedback loops are the cause of waste.