Restoring (regenerative) logic
Beginner
Logic that cleans up a slightly wrong signal, so small errors shrink as they pass through gates instead of growing.
Novice
Each gate has a gain greater than one in its switching region and less than one near 0 and 1, so a slightly degraded input produces an output closer to the ideal 0 or 1. A chain of such gates restores full logic levels.
Expert
Follows from in the transition region of the VTC and in the valid regions. It is why static CMOS tolerates noise stage after stage and why the cross-coupled inverters of a latch or SRAM cell snap to a stable state.