Process control simulation is used to predict the results of a process with chosen variables in a computer simulation.
You can kick a ball and then describe the physics of the action mathematically. The weight of the ball, the force and direction of the kick and the friction of the ball on the ground can all be modeled and programmed into a computer simulation. Once the computer model has been produced, then the weight of the ball and the other variables can be change and a precise predication can be made about the location at which the ball would land, if the ball was a certain weight and the kick was at a certain force.
Process control simulation can be used to model and predict the results of very complex variable adjustments. For example, the complex processes of a chemical plant can be modeled into a computer simulation and the effects of certain adjustments can be predicted by the computer model for testing purposes instead of being set up in the real world.