Theories of mental representations in general, and mental models in particular, deal with form and function of individual knowledge. The central question is how human beings represent information mentally, and how they use that information to interact with the world in adaptive ways. Users knowledge about computer systems are a specific type of mental representations. Mental representations have been investigated by researchers in philosophy, cognitive psychology and more recently cognitive science.
Sources: Mental models: a gentle guide for outsiders, What’s Your Idea of a Mental Model?, Eliciting and Describing Users