Variable Intake Air System Control Solenoid. This signal introduces the intake manifold vacuum into. I misspoke in the video calling this a variable valve timing or vtec mechanism.
Using inputs from various engine sensors (engine speed, coolant temperature, camshaft position, etc.), the ecm controls the camshaft position using pulse width signals (duty signals) to four solenoid valves. That valve is what makes necessary adjustments to airflow to the engine and maintains a smooth idle. This signal introduces the intake manifold vacuum into the power valve actuator and therefore closes the power valve.