Compression reduces the dynamic range of the input signal. Downward compression takes all sounds above a specified threshold and brings them downward. You can compensate for volume drop via makeup gain.Upward compression isn’t feasible (would just raise noise floor). Put a bit of compression on your “Master bus” or across the entire mix. It’ll help ‘glue’ things together.LimiterAn aggressive compressorPluginsNoise reduction, stereo imaging, etc.
Saturation: A hot signal recorded to tape oversaturates it giving it additional harmonics, character and “grit”, and can be emulated with digital plugins.
To make a kick sound more present, INCREASE the attack (in ms) so that it’s not grabbing the first part of the sound so aggressively. Then use the release control to adjust how much you want to hear the rumble after the strike.
A limiter is just a simple compressor that pulls your overshoots back aggressively.
This one is often used to do the opposite of what it sounds like. You can use it to “boost volume” without clipping since it will raise the RMS average but “limit” the top end.