Feedback loops help maintain homeostasis by allowing the organism to respond to changes in its environment. Feedback loops are important because organisms are always dealing with changes in environment or internal condition, so the feedback loop prevents those changes from going too far and becoming dangerous.
There are two types of feedback loops, negative and positive. Positive feedback loops occur when the result of the loop signals to the organism to do the loop more. Negative feedback loops occur when the outcome tells the body to slow down or stop. Many metabolic processes contain negative feedback loops that are based on the product of the process. When the concentration of the product is high enough, it shuts down the process.
One well-known negative feedback loop that maintains homeostasis is associated with thermoregulation. When an organism is physically active, the metabolic processes necessary to move result in a higher body temperature. In humans this temperature is detected by receptors in the brain and skin. Once it is detected, the body responds by sweating which helps lower its temperature. The blood vessels near the skin surface dilate, and the lowering body temperature gradually turns off the physical response as it returns to normal.