Parasympathetic Nervous System, PSNS
The PSNS is a branch of the Autonomic Nervous System, ANS.
Together with the Sympathetic Nervous System, SNS, with which it work in tandem but in opposition, it helps to control our endocrine glands, internal organs and vegetative functions. The PSNS brings about quiet resting states in the body and allows energy to be stored up.
Please see the entry for the Autonomic Nervous System for further details about the functions of the PSNS.