#1
Well the title says it all, what does it do?
So that with good courage we say, “The Lord is my helper. I will not fear. What can man do to me?”

-Hebrews 13:6
#2
It lowers the dynamics to level out the waveform. EX get rid of annoying volume peaks when you hit a note really hard.
Quote by Venice King
Beethoven ****ed Jimi Hendrix and I was born. I make my own music.
#3
Quote by Ghast
It lowers the dynamics to level out the waveform. EX get rid of annoying volume peaks when you hit a note really hard.



^This, in a nutshell.

It evens out the extremes of the signal in order to make the notes you play sound more even. One note doesn't sound particularly louder or softer than any other note. Of course, if you overdo it with a compressor, it makes your notes sound like they are being choked to death and your tone sounds like crap. Because of the way bass strings vibrate (large variations in the vibrations because they are so thick and tuned to such low frequencies), a compressor is a very commonly used bass effect.