To answer the origional question its just a one way valve between the crankcase and the intake. The valve is a replaceable piece that sits under that pcv cover and is held in place by a spring. It allows the crankcase to vent so that it doesn't pressurize and blow oil out of all of the seals. If I remember right the bottom of that hole is connected to the crankcase and near the top is a hole going to the intake. Valve sits between those.