User interface (UI) prototyping is an iterative development technique in which users are actively involved in the mocking-up of the UI for a system. UI prototypes have several purposes:

• As an analysis artifact that enables you to explore the problem space with your stakeholders.
• As a design artifact that enables you to explore the solution space of your system.
• A basis from which to explore the usability of your system.
• A vehicle for you to communicate the possible UI design(s) of your system.
• A potential foundation from which to continue developing the system (if you intend to throw the prototype away and start over from scratch then you don't need to invest the time writing quality code for your prototype).