A Definition

Dictionaries have many explanations for "model." Encarta provides the following, among others: "Simplified version of something complex used, for example, to analyze and solve problems, or make predictions."

Models can consist of drawings, mock-ups, maps, formulas, computer programs, and other written or tangible forms. They help us think better by reducing the amount of information we need to keep in mind about a problem. Our brain works better when it is not overwhelmed with input.

The key to successful modeling is to extract from reality (and include in the model) only those aspects that are most relevant for answering the questions at hand.