“A mental model represents a person’s thought process for how something works (i.e., a person’s understanding of the surrounding world). Mental models are based on incomplete facts, past experiences, and even intuitive perceptions. They help shape actions and behavior, influence what people pay attention to in complicated situations, and define how people approach and solve problems.”
Users create mental models very quickly - often before they even use a website or a product. Users’ mental models come from their prior experience with similar sites or products, assumptions they have, things they’ve heard others say, and also from their direct experience with the product or device. Mental models are subject to change.