It does have to do with oil. The vapor from the oil being spun around in the crankcase is vented out through here and burned in the intake manifold. The hose he is talking about is the one connected to the valve cover that runs to the intake pipe. It sucks oil into the hose, through the valve cover and out through the PCV hose to be burned in the intake manifold. So it goes in a complete cycle through the engine to make sure stale oil vapors are cleansed from the system to avoid contamination and excessive pressure. Get a catch can and you will see the nasty oil vapor being shot through that hose after just a quick drive around the block.