[Rapture] Huge dilemma as to how velocity affects envelopes

I've been doing hours of experiments. I read Rapture Manual and Simon Cann's book.
 
I don't understand the difference between Velocity Track and Velocity Intensity when it comes to these affecting the Envelopes. I really see no difference.
 
I know they act differently in Pitch, Cut Off, Resonance and Amp. But still I DON'T UNDERSTAND.
 
If anyone could enlighten me, I would appreciate it very much.