Paper prototyping offers great benefits in terms of saved time and cost since it enables developers to test product interfaces (from software and websites to cell phones and microwaves) before they write code, or begin development. This also allows for easy and inexpensive modification to existing designs. Iterative usability testing of prototypes leads designers and developers to a progressively bug-free interface, which they can then develop with a fair amount of confidence.
The method itself involves creating rough, even hand sketched, drawings of an interface to use as prototypes, or models, of a design. These prototypes can then be tested on users by asking them to perform some tasks using the roughly sketched out interface, while designers observe their actions to gauge where they face problems, and what they like. Though seemingly unsophisticated, this method is very successful at discovering usability issues early in the design process.