Limiter
The primary function of the Limiter is to prevent the audio signal from exceeding a certain threshold. It does this by reducing the gain of the signal whenever it goes over.

Parameters
Send Level
Reduces the gain of the audio input to the effect. Unlike adjusting Dry / Wet, modulating send level preserves any audio tails.
Pre Gain
Sets the level of the signal before it hits the limiter. This is useful for boosting the level of a signal without clipping, or for preventing a signal from clipping when it is too loud.
Threshold
The ceiling, in dB, that the signal will not be allowed to exceed.
Release
The time it takes for the gain to return to normal after the signal falls below the threshold.