PROTOTYPE:

A prototype is an original type, form, or instance of something serving as a typical example, basis, or standard for other things of the same category. In many fields, there is great uncertainty as to whether a new design will actually do what is desired. New designs often have unexpected problems. A prototype is often used as part of the product design process to allow engineers and designers the ability to explore design alternatives, test theories and confirm performance prior to starting production of a new product.

Sketching User Experience