What does variable valve mean?

[Lee]

Automobile engine valve timing mechanism and technology, also known as continuous variable valve timing system, is commonly equipped in today's high-performance engines. Function of engine valves: This system optimizes the engine's air distribution process by adjusting the cam phase or valve lift through its equipped control and execution system. Operating principle: Since the valve timing angle significantly affects engine economy and power at both high and low speeds, the system opens valves early and closes them late at high speeds to utilize intake inertia for increased air intake and scavenging efficiency, while the opposite applies at low speeds.