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Since the natural environment is so complex, we have to simplify it in some way in order to portray or understand it. Representations of reality are called models. We are all familiar with scaled-down models of ship or aircraft, which we can physically construct; these are examples of hardware models. The term 'model' can also be used to describe conceptual idealizations of reality, such as a hypothesis, a law or a theory. The definition of a model proposed by R.J. Chorley and P. Haggett is that it is 'a simplified structuring of reality which represents supposedly significant features or relationships in generalized form'. In recent years geographers have been making considerable use of models in the application and development of theory: this is a trend, which was first apparent in economic geography in 1950s, but has now spread to physical geography.

Models used in physical geography vary widely in the amount of abstraction of reality in them. Some hardware models, such as large tank models of rivers, estuaries, and coasts, are also iconic models, closely imitating the real world in all respects but that of scale. Much more widely used are analogue models, which represent the real world by other properties. A kaolin model of a glacier, and a map, are both analogue models. Mathematical models in particular have become very important in geographical research since they can be used to predict changes.

Since they help us to organize and explain data, models are obviously very useful teaching and learning aids. Models should also help to identify gaps in our knowledge and point the way to further work. Models are simplifications of reality, and they are often very attractive; there is always the danger that they might be substituted for and accepted as reality. Also, since reality can be simplified in many ways, it is important that any model is considered as but one possible way of viewing the real world.