In UML modeling, you can use connectors to join the diagram elements in a diagram. A connector is the actual line in a diagram that represents an underlying semantic relationship. Although you can connect diagram elements by using any of the connectors in the Palette, a semantically correct UML diagram requires the use of specific connectors in specific circumstances.
The connector is displayed between the diagram elements and the corresponding relationship is added to the model. The relationship is displayed in the Model Explorer view if you expand its container and you do not filter its type.