..[#f1] The arrow indicates a ‘has-a’ relationship. The object attached to the arrow head ‘has-a’ instance of the other. The numbers next to the arrows indicate the multiplicity, i.e. object A has n to m instances of object B. The difference between a UML association and aggregation is not conveyed in any diagrams. To UML aficionados, I apologize. Word is not the best drawing tool.