Increase battery life
Reduce power consumption
Reduce thermal output
Reduce the voltage suppiled to the processor
A reduced voltage decreases power consumption and thermal output of the processor - improving battery life
Preventing thermal throtteling - allowing longer sustained performance
Undervolting is only compatible with Haswell and Broadwell processors (Macbooks from 2013 - 2015). This functionality has been prevented on later generations.
Disable the automatic overclock to save power when performance is not of priority
Set a definitive power limit, constraining the CPU to perform within a set power boundry