A computer model is an abstract mathematic representations of a real-world event, system, behavior, or natural phenomenon. A computer model is designed to behave just like the real-life system. The more accurate the model, the closer it matches real-life. 
A computer model is a translation of objects or phenomena from the real world into mathematical equations.
Thanks to https://www.igcseict.info for the content below. A model might be used:
- To test a system without having to create the system for real (Building real-life systems can be expensive, and take a long time)
- To predict what might happen to a system in the future (An accurate model allows us to go forward in virtual time to see what the system will be doing in the future)
- To train people to use a system without putting them at risk (Learning to fly an airplane is very difficult and mistake will be made. In a real plane mistakes could be fatal!)
- To investigate a system in great detail (A model of a system can be zoomed in/out or rotated. Time can be stopped, rewound, etc.)
Do I have a model?
- I have identified important features of whatever events I hope to represent.
- I identified rules that control those features and their relationships.
- I have expressed those rules with math.
- I have adjusted for how likely each factor is.
- Define the term computer modelling.
Give an expected result of an upcoming action or event.
Observe, study, or make a detailed and systematic examination, in order to establish facts and reach new conclusions.
Give the precise meaning of a word, phrase, concept or physical quantity.