Maintaining a consistent internal environment is essential to all living organisms. Achieving balance through a tightly regulated set of processes requires constant sensing and manipulation of changing physiological situations. A homeostatic feedback loop is such a process that maintains balance by linking continuous monitoring of a physiological parameter to response systems that can counteract detected fluctuations.
For humans, example parameters kept under tight homeostatic control include blood glucose concentration, core body temperature, blood pressure, and blood volume. Knocking any one of these parameters out of tolerable range is fatal. While maintenance is vital, we expect parameters to oscillate around a baseline level as they are often under the control of two effector processes, one producing an increase and the other, a reduction. Both neural signaling and hormone secretion play a part in controlling homeostatic parameters. These mechanisms vary by the target system involved and the speed of response required.
Negative feedback loops are those that serve to move a parameter closer to a state of homeostatic equilibrium. They are stabilizing processes that are triggered to readdress balance when a system deviates from a baseline state. Positive feedback loops are less common in humans and are those that create change and disrupt the balance in a body's system. With this in mind, it's clear that most processes involved in homeostasis are negative feedback loops as the goal of control is to maintain internal equilibrium.