DVFS
Beginner
Slowing the chip down, and turning down the electrical push that runs it, when there is little work. It saves battery.
Novice
Dynamic voltage and frequency scaling: lowering the chip’s supply voltage and clock speed while it runs, whenever the work allows. Switching power grows with the square of voltage, so a small voltage cut saves a lot.
Expert
Needs characterized voltage–frequency operating points, regulators that can change voltage on command, clock switching or PLL relock, and timing signoff at every supported pair, often separately per domain.
Explained in Personal and edge devices (Industries).