* wehrmacht,

different channels: PCM (pulse code modulation) cares about the internal signal, means you are changing the volume "before" it leaves the soundcard. "Front" and others are the output channels.
I wonder why your output is named "Front": That's normally the output jack where you put in your head set. Do you see "Master"?
Anyway, it doesn't really matter which one you use, as long as you don't record things.

Uwe