People understand and interact with systems and environments based on mental representations developed from experience.
A mental models is a compression of how something works. They reveal key information while ignoring irrelevant details. They concentrate the world into understandable and usable chunks. We cannot keep all of the details of the world in our brains, so we use models to simplify the complex into understandable and organisable chunks.
But you don’t just learn a micro lesson that applies in one situation. Instead, you draw a general abstractions, one that tells you to check before touching anything that could potentially be hot.
Of course we don’t need to know all of the details, but we know what’s important. But we also apply our understanding of gravity in other, less obvious ways.
Different people may hold different mental models of the same item. Single person might have different models of the same item, each dealing with a different aspect of its operation.