what is the ratio part, what does it mean how does one use it?

anyone?

Would it be a bad idea to have a compresser on the master channel coz ive done that on a track i'm working on an the kick & bass sounds nice and it doesnt seem to have effected the synths, or hi hats etc? will that give me problems?


( I feel like that metal bastard from short circut "need imput" hahaha)