The term affordance refers to the relationship between a physical object and a person (or for that matte, any interacting agent, whether animal or human, or even machines or robots). An affordance is a relationship between between the properties of an object and the capabilities of the agent that determine just how the object could possibly be used.
<aside> 💡 Affordance is not a property, it's a relationship.
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Affordances determine what actions are possible. Signifiers communicate where the action should take place. We need both.
<aside> 💡 The affordance of touching exists on an entire screen for instance, and the signifier indicates where the touch should take place.
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Mapping is a technical term, meaning the relationship between the elements of two sets of things. Suppose there are many lights in the ceiling of a classroom and a row of light switches on the wall at the front of the room. The mapping of switches to light specifies which switch controls which light.
Feedback is communicating the result of an action. It must be immediate.
A conceptual model is an explanation, usually highly simplified, of how something works. It doesn't have to be complete or even accurate as long as it is useful. The files, folders, and icons you see displayed on a computer screen help people create the conceptual model of documents and folders inside the computer, or of apps or applications residing on the screen, waiting to be summoned.
When people use something, they face two gulfs: the Gulf of Execution , where they try to figure out how it operates, and the Gulf of Evaluation , where they try to figure out what happened. The role of the designer is to help people bridge the two gulfs.