A critical component of learning a new skill is the storage of massive amounts of information and the ability to retrieve that information with increasing ease.  Experts have simpler but more effective and more richly related knowledge about a domain or situation than do novices, who may know more facts but fewer useful relationships among them.  Thus, a key to the evolution of expertise is the evolution of representation: as expertise increases, knowledge is represented in a more abstract way, reducing the need to manipulate massive amounts of information.

People use Mental Models every day to make decisions.  Mental Models help them determine which information is important to the decision at hand and how that information should affect the decision.