Generally, use cases are created to specify different types of actors (users) that will be using the application and their various types of interactions with the system.
Using Figure 1 as an example, I want to share with you a use case diagram for an electronic voting system.
Project Update: PrivateReview Use Case Diagram Example
Below in Figure 2, you can find a simple use case diagram for my project. The primary design is focused only on one actor – the user, but with time, there may be other actors, such as friends that may be able to view your reviews and provide their comments.