What does a use case diagram do?

A use case diagram serves as a visual representation of the interactions between users (actors) and the system to achieve specific goals. It provides an overview of multiple use cases, illustrating how various functions or scenarios interact with different actors in the system. This capacity to represent several use cases at once makes it a useful tool for understanding the functional requirements of a system and how different parts of the system relate to one another.

In contrast, a diagram that focuses on a single use case would not encompass the broader interactions that a use case diagram typically captures. Similarly, connecting use cases to class diagrams is a different aspect of design that does not relate specifically to the purpose of a use case diagram. Lastly, while listing use case goals may be helpful, it falls outside the primary function of a use case diagram, which emphasizes visual relationships over textual listings.