LDO regulator
Beginner
A small circuit that takes in electricity with a wobbly push (voltage) and turns it into a steady supply for the chip.
Novice
Low-dropout regulator: a linear voltage regulator that outputs a stable voltage slightly below its input. Simple and fast, but it wastes the voltage difference as heat.
Expert
Efficiency is roughly , so a large input range costs power. Used on-die to clean up supply noise or to absorb a supply that varies with location.