The Limiter is a device used to prevent signals from going over the threshold level. Commonly used in mastering as the final glue for a song and to increase the loudness. When used in Digital mode with Attack at 0 it functions as a brickwall limiter.
Set the level the detector signal must pass over for limiting to begin. When the detector signal is below the threshold audio is unaffected. When the detector level surpasses the threshold limiting is applied and the input signal will be capped at the threshold.