A simulation is an imitation of some real event or device. It is often used interchangeably with the word modeling (as in modeling of natural systems). A simulation tries to represent certain features (or behaviors) of a complex physical system based on the underlying computational models of the phenomenon, environment, or experience.

Simulations are used to understand the operation of real-world, practical systems; for instance, the modeling of natural systems such as the human body. They can be used to simulate a certain type of technology, such as a new type of airplane, or model an engineering concern, such as the stability of a building during an earthquake.