PJ Raia

Reading the description of the modifier Penetrating in the Champions Complete rulebook, I'm either a bit slow, or over-thinking it because exactly what the advantage is and does escapes me. I'm all ears if someone can break this down for me. Thanks in advance. 

New aboard here, so forgive me if you've (likely) read this umpteen-times over as it seems like it would have come up before, but I haven't been able to find it yet: how does one determine how fast a character moves in miles per hour?