Explain the different elements of a Use Case ?

Package: - It logically groups element of a UML model.
Use Case :- It represents a set of events.
Actor : - Role played by an outside object.
Interface :- It specifies the externally operations of a class, component, package, or other element without specifying internal structure.
Communication: - How an actor Dependency shows relationship between two elements.
Extends: - Indicates that the elements come in parent child relationship where one element inherits other elements behavior.
Uses: - Here one element uses the other elements behavior. The main difference between Extends and Uses is a “Is a” and “Has a” relationship. “Is a” relationship defines a child parent relationship. Example “XYZ” is a child of “PQR”. “Has a” relationship defines an aggregation relationship that “XYZ” has a “BLUE SHIRT”.
System boundary: - Indicates the system boundary of a Use case.
2-Element Constraint: - It shows a constraint on two classes or associations.
OR constraint: - It shows an OR constraint on two classes or associations.