Think of a train set - a really good one. With rails, trees, scenery, stations, signal boxes and of course the trains themselves going moving around the track.
What you have in front of you is a 'model'. The model tries to behave in the same way as the real thing. The more accurate the model the more realistic it behaves.
The train set is an example of a 'physical' model.
And they are very popular in all kinds of areas.
For instance the Royal Navy has one to model the sea. They want it because they need to see how a new ship is likely to behave in real-life. It consists of a huge tank of water, bigger than a swimming pool, with waves created by huge mechanical paddles. Then they carefully construct a scale-sized model of a new ship design and place it in the tank and see how it behaves.
This is a lot cheaper than building a full size ship only to find out there is a problem with it.
However, physical models are not the only ones available.
'Mathematical' models are also popular. In your physics class you know that an object's behaviour can be worked out using equations. For instance the speed, acceleration and flight path of a ball traveling through the air can be modelled using (relatively) simple equations.
The model may allow you to change the ball's size, weight, starting speed and so on (formally called the models' 'initial conditions'). The equations are run for a period of time and tell you the likely location and speed of the ball at any point in time.
This is the true power of modelling - it allows you to predict the future.
If you know the starting conditions and everything relevant about the object's behaviour then you have a chance of creating an excellent object model.
This mini-web takes you through some of the object models in use today.