Prototyping
Prototypes
A prototype is a simplified version of a final product. Prototypes are produced because they can give all the stakeholders (people with an interest in a product) a good idea of what the final product might look like very quickly, without having to wait it to be completed fully. They can then make useful comments that can be used when the real product is actually designed and built.
For example, if you had to write a user interface for a software product, if might take you a month to write a program that does what you think it should, or it could take you a day to knock up something in PowerPoint that looks like the user interface, even if it doesn't actually work! The first method, which took you a month, was expensive to produce and you may have to do a complete redesign anyway if your original ideas were not what the customer was actually thinking of. The second method, which took only a day, produced something that may not actually work but did illustrate what you were intending to do. If you show this prototype to a customer, they can then give you valuable feedback before you then proceed and spend a month actually writing the software properly.
Rapid Application Development (RAD) is a Systems Life Cycle that makes use of prototyping. You produce a prototype, get feedback from your users, use this information to improve the next prototype, get more feedback, produce another improved prototype and so on in an 'iterative' process, until you have a final product.