To be healthy, the human body must maintain equilibrium in its many systems — e.g., levels of water and minerals in the blood, blood pressure, absorption of nutrients and removal of waste products from cells. This is called homeostasis.
The body's heat regulation system is another example of a homeostatic system. As the internal temperature rises, the body sweats to cool off. Alternatively, when the body gets very cold, it starts to shiver to generate some heat. The goal in both cases is to bring the internal temperature back to 98.6 degrees F.