i think trial and error after reading a bit would be a lot better though.
the purpose of compression is to recreate what the ear hears. what a mic 'hears' can peak and transient in ways the ear would hear more even.
compression has attack, release, threshold, ratio, and makeup gain.
okay...say a wave comes into your compressor at 8 db. your threshold is set to 10. the compressor does not pick up.
same wave of 8db comes in and the thresh is at 6db. ok...so when that wave arches over the 6db mark, it will decrease that volume at a ratio of whatever you set it to. say its 2:1. ok...so for every 2 db's it is over it will decrease it to 1 db. so...4 db over...2 db...6 db over...3db.
but how fast will it start doing that? that's where your attack comes in. if it is set to .5 seconds, .5 seconds after it breaks the threshold it will start compressing the db's according to the ratio.
how fast will it stop compressing? that's the release. usually this will be higher than the attack. basically always. you adjust the attack according to how normal it sounds....but if its something short like a snare...you're going to want a short attack. if its something you want sustained...you may want the release long.
during this whole process the compressor has been lessening the peaks, and you can up the volume by using the makeup gain to "make up" for the lost volume.
that's compression in a nutshell