Explain Variable Valve Timing (VVT) and its benefits.

VVT adjusts the timing of intake and/or exhaust valve opening relative to crankshaft position based on engine speed and load. At low RPM, valve overlap is minimized for smooth idle; at high RPM, overlap increases for better volumetric efficiency. Methods include cam phasers (hydraulic or electric), cam profile switching (like Honda's VTEC), and fully variable systems. Benefits include improved power across the RPM range, better fuel economy, and reduced emissions.