multi-Vt
Beginner
Using a mix of fast switches that leak a bit of power and slow ones that leak less, picking the right kind for each spot.
Novice
Building the same logic gates in versions whose transistors have different threshold voltages (the voltage at which they switch on). Low-threshold gates are fast but leak more current; high-threshold gates are slower but leak much less. Designers mix them gate by gate.
Expert
Synthesis and leakage recovery assign a flavor per cell under timing constraints: low- only on critical paths, high- everywhere with slack. The best mix shifts with corner and temperature, so leakage is signed off hot.
Explained in Personal and edge devices (Industries).