Prototyping is trying out your idea in a real way but cheaply and quickly. People do not give real feedback on hypotheticals, so it’s better to present them with a concrete idea. Often a sketch suffices because all the components of your idea have to be present together for someone to give real feedback.
a. Function Prototype:
i. Demonstrates how the product would function so the user can interact with it.
b. Form Prototype:
i. Demonstrates the overall “form” of the product so the user can feel and see the feasibility.
ii. Example: The original step for the Palm Pilot was toting around a block of wood to see if people would interact with the shape of the product.
c. Experience Prototype:
i. Anything that causes people to suspend disbelief.
ii. Example: Intel Health Care video crafted a believable world so people could understand how the product idea works.
d. Landing Page method:
i. See if people interact with the site and include ways for people to express their interest.
e. The 404 Test
i. Of your true customers, who would be interested enough to click on a link even if it doesn’t go anywhere? This is a way to monitor customer curiosity and interest.
f. The Concierge Method
i. “How disappointed would you be if you could no longer use this product?”
g. The “Wizard of Oz” Method
i. Fake the backend but allow people to still have the experience
Here is a useful link about prototyping in design: http://www.innovate-design.com/prototyping-process-2/
And this link goes into further depth about form, fit, and function prototypes:
http://leardon.com/form-fit-function-prototype

Low Fidelity / Interactive UI Prototypes
Designers who start with a pretty prototype often overcommit to a design before testing its individual components. Low fidelity, interactive prototyping avoids this by allowing the user to test the experience without wasted time and effort on the designer’s part. Furthermore, the lack of color and detail directs users to the components themselves and the functionality of the app. With pretty prototypes, users might be tempted to judge the product based on its aesthetic qualities.

After the designer hands the user a prototype without instructions, she can observe what they choose to do, listen to their their feedback, and quickly change components to test alternative options in real time.

An example of low fidelity prototyping: https://www.youtube.com/watch?v=yafaGNFu8Eg

Contributed by Amelia Miller, Maria McLaughlin, and Maia Suazo-Maler.