The hose you're talking about is a ventilation tube that's part of the PCV system. The crankshaft creates the "wind" necessary to push the oil fumes out of the crankcase, into the hose you're refering to, and back into the incoming charge of air through the air cleaner.
If there is an excessive amount of oil coming from the tube into the airbox, you have what's commonly referred to as "excessive blow-by". In layman's terms.....your engine is old and has high mileage or has not recieved the proper maintainance required. If it's just "air", nothing to worry about.