The Parasympathetic Nervous System is a part of the autonomic nervous system that helps the body relax and conserve energy. It is often referred to as the "rest and digest" system because it promotes functions that occur when the body is at rest, such as digestion and lowering heart rate. When activated, the parasympathetic nervous system counteracts the sympathetic nervous system, which is responsible for the "fight or flight" response. This balance between the two systems is essential for maintaining homeostasis, allowing the body to respond appropriately to stress and return to a state of calm.