A simulation is an imitative representation of a process or system that
could exist in the real world. In this broad sense, simulation can often be
used interchangeably with model. Sometimes a clear distinction between the two
terms is made, in which simulations require the use of models; the model
represents the key characteristics or behaviors of the selected system or
process, whereas the simulation represents the evolution of the model over
time. Another way to distinguish between the terms is to define simulation as
experimentation with the help of a model. This definition includes time-
independent simulations. Often, computers are used to execute the simulation.