I know nothing about compressors

[sangha]

A compressor - reduces the volume of what's passing through it whenever the volume goes above a certain level, known as the threshold. How quickly it reduces the volume, and by how much depends on the settings of the Attack, and Ratio controls (and "knee" if your compressor has it).

Most often used to even out the dynamics of a track in order to beef it up and raise it's avg level. Also used on masters and groups to get things to fit together better

A soft clipper - Basically a comp/limiter that emulates analog clipping. Usually, they add some distortion. Generally used to color a sound. Not generally used to shape the dynamics of a track, though it can be used to shape the dynamics of the notes.

A maximizer - meant to maximize the level. Generally compression but if I understand them correctly, they also use eq. Generally used as a mastering tool, according to what I've read about them (Note: I neither own nor have used a maximizer)

A limiter - a form of compression where the reduction in volume above the threshold is more drastic (ie a higher ration - limiting is considered to start at ratios of about 10:1). Used to prevent going over 0db and to remove the highest volume peaks. Often used much like a compressor, but with a more drastic effect on the peaks.