PCV Valve Question

Hey,

I am thinking about putting an oil catch can on the GTP after seeing how gummed up my throttle plate is. Usually I guess you put those on the line that goes to the PCV valve? Does the PCV valve even do anything on our cars? I was thinking about the design and because they're not even hooked up to a hose, I have no clue how to begin to imagine how they even work on our cars? Anyone care to fill in the numerous mental gaps for me?...

The PCV valve on the L67 engine is used and not for decoration. It is just directly mounted on the supercharger which is technically the upper intake manifold.

I guess what is confusing me is the fact that it just sits down in that hole and there's no tube connected to it to flow through or anything. How does it work?