The design process creates a set of models used to describe the system. These drawings and descriptions are the blueprints used to create the final product. Imagine a set of blueprints for a house, or electrical schematics for a computer. In both cases, you can imagine a set of drawings that completely defines the product to build. Each set of drawings also has its own set of symbols that are unique to the profession in which they are used.
Software modeling is no different.
Although you will ultimately create a complete text-based set of use cases, the first artifact that you create in the modeling process is the use case model. This model is a visual representation of the actors and the use cases. Although this model is extremely simple, I have found that it serves as an invaluable graphical overview of the system. To create the use case model, we use the UML symbol for an actor, and the UML symbol for a use case. Figure 1 shows these symbols.