"Once you understand business models you can then start prototyping business models just like you prototype products." -Alexander Osterwalder
The concept of a prototype is a cheap test of several of the key assumptions of an idea. A prototype succeeds when it demonstrates the essential characteristics of the idea, capturing the aspects that are crucial for the final idea to succeed. The super soaker prototype to the right was a test of the key idea of a hand pump to pressurize the water.
Rapid prototyping refers to having a mentality of looking for ways to get quick prototypes out the door, even when they don't perfectly match the desired use case. The idea is that many small test cases iterated through quickly will map the space more efficiently than preparing a single large test. The super soaker prototype, for example, was constructed with off the shelf components rather than anything that needed to be custom built.