The professor fills an empty pickle jar with golf balls, pebbles, and sand to demonstrate to his philosophy class how to prioritize the important aspects of their lives. The golf balls represent family, health, and relationships, while the pebbles are other important things like career and home. The sand is the small unimportant stuff - if you fill your life with small things first there is no room for what really matters. The lesson is to focus first on the golf balls and pebbles, and manage your time well, though there is always room for chocolate milk or pleasure.