Idq is the bias current i.e the current flowing in the drain when no RF is applied to the input. Id is instead the actual current when a given RF signal is applied to the gate.
this is a power HF GaN transistor with input matching network.
Sadly I´m not familiar with HF components.
But did you read the "Application Note: GaN Bias Circuit Design Guidelines"
Don´t if this provides more information than the video.
Idq is the bias current i.e the current flowing in the drain when no RF is applied to the input. Id is instead the actual current when a given RF signal is applied to the gate.