When we understand something—let’s say a concept, like a table—we have some formulation of that “in our head”. That formulation is something we can manipulate while we’re thinking or conversing or acting.
Designing for the Models in our Heads
What is a model?
Models—good ones, anyway—are valuable in a number of ways.
The best resource I know on the topic is the paper Models of Models by Hugh Dubberly.