The Elements of Use Case Diagram
Use case diagrams are very simple in nature, describing two types of elements: Let's take a closer look at what constitutes a use case diagram.
Actor portrays any entity (or entities) that perform certain roles in a given system. The different roles the actor represents are the actual business roles of users in a given system.
Use case in a use case diagram is a visual representation of a distinct business functionality in a system.
System boundary defines the scope of what a system will be. A system cannot have infinite functionality. So, it follows that use cases also need to have definitive limits defined.
Relationships - there are 5 relationships in a Use Case Diagram they are
Association between Use Case and a Actor
Generalization between Actors
Generalization between Use Cases
Include Relationship between Use Cases
Extend Relationship between Use Cases
