Norman introduces the concepts of affordances and signifiers to explain how design communicates usage to users. Affordances suggest possible actions, while signifiers indicate where actions should occur. For example, a door with a flat plate suggests pushing, while clear signage ensures users understand the action if the affordance is not apparent. Norman elaborates, "Affordances determine what actions are possible. Signifiers communicate where the action should take place." These tools are essential for intuitive design.