The Limiter limits the level of the audio signal by preventing the peaks from hard clipping. It works by reducing the level of the sound when it's above a threshold of 0dB to a level of 0 dB. This makes it possible to increase the input gain to make the sound louder and still keep it from hard clipping.
Input Gain - The amount of gain applied to the input signal.
Attack/Ahead - The time it takes for the limiter to start working. When Look Ahead is enabled, it's also the amount of time it looks ahead and analyzes the input signal. Note: the look ahead time is actually the amount of time the signal is delayed.
Release - The time it takes for the limiter to stop working.
Look Ahead - When Look Ahead is enabled, it functions as a "brick wall" limiter, otherwise some of the signal may be above 0 dB and be clipped.
Soft Clip - How soft the clipping is. It will hard clip when it's set to zero. The LED shows when it's hard clipping. This is only available when Look Ahead is disabled. Note: it's not necessary to make it so it never hard clips. The more it's soft clipped, the more the audio signal below 0 dB is changed.
Output Gain - The amount of gain applied to the output signal.
Reduction Meter - Shows the amount of gain reduction.
Output Meter - Shows the output signal level. When Look Ahead is disabled, it shows the output signal level before the soft clipper. For stereo sounds it shows the loudest channel.
If it's limiting too much, try lowering the input gain.
If it doesn't sound natural when the limiter is attacking, try increasing the Attack/Look Ahead time.
If it's "pumping" or "breathing", try increasing the Release time.