#1
sorry the noob question... but I really can' figure out what is the function of a compression effect... someone can explain to me? thx in advice
I have:

Gibson les paul classic
Yamaha RGX-420S
Stinger STP 25GOR
Digitech DF-7
Digitech Digidelay
Digitech rp-80
#2
A compressor is a device that levels out signal dynamical by making loud parts quiter and quieter parts loud
#4
Read the FAQ, yes

It limits your dynamic range, but that too much.
So you get really long sustained notes, or really prominent solos
remember, when you use one, if you can hear the compressor at work, you are overusing it .