The coffee can is a vacuum reservoir. It's there to keep a constant amount of vacuum for your engine. If you do not have a diagram on the inside of your hood or right in front of the radiator then you'll need a book. YOu really should have one. They're about 20 bucks at the auto parts store.
I have the full shop manual but it negates mentioning many of the side items on my engine. Does anyone know where the other end of the hose to the right valve cover goes? It splits in a Y at that point and continues down stream.