The document discusses different types of prototyping used in interaction design. It describes explorative prototyping which is used to explore system requirements with users, experimental prototyping which assesses if a planned system will be adequate, and evolutionary prototyping where a design evolves through multiple generations. Prototypes can be horizontal, covering many features with little functionality, or vertical with fewer features but more fully described. Prototypes are used to get feedback, explore requirements, and ground discussions. The prototyping process involves following design patterns, creating prototypes for user stories, and iterating the prototypes and stories.