This document discusses prototyping for user experience design. It defines prototypes as approximations used to communicate ideas and explores why they are useful, such as enabling quick identification of mistakes. Common prototyping tools are examined, including paper, office software, drawing tools, and specialized prototyping programs. Six key principles of prototyping are outlined, such as aiming to finish a prototype in a day and borrowing designs liberally. The document provides resources for further prototyping information.