"Simulation of any system implies a mapping from observable aspects of the system to corresponding symbolic elements of the simulation." (H. H. Pattee, "Simulations, Realizations, and Theories of Life", in Artificial Life) For Pattee, realizations are functional replacements. They are judged primarily by how well they function as implementations of design specifications. (Thus a building would be the implementation of a blueprint) 

What is the relation between simulation and representation? In a famous passage on simulacra, Jean Baudrillard contrasted the map that serves as a representation of an existing territory, with a map that precedes it — in which the map comes first and begins to shape the real world. For example, we might say that while a flight simulator has no underlying reality, fighter pilots can only fly supersonic planes in the real world because they can train their minds and bodies in a simulation first. Simulation in its most generic sense, is the point where the imaginary and real coincide, where our capacity to imagine certain kinds of futures coincides with our capacity to predict and produce them in advance. Simulation, we could say, is the panoptic imaginary. Simulation, is about the hyperreal and the flrctional' The hyperreal doesn't have a history, it has a "future past," an imaginary history that is over before it begins. (William Bogard) Simulation always aims for the "more real than real"; as a technical operation, it works to eliminate, not foster, illusion.

"The study of dynamical systems by computer often blurs the distinction between theories and simulations." We could call this SimScience -- the use of fractals in the earth sciences, for example, underscores the differences between simulation and inferences about process, between description and explanation

The new capacities for simulating images, video and audio will emerge that will flood the internet with artificial content. Their impact, combined with micro-targeting will be very powerful, and make it difficult to trust media. The constant flood of views, opinions, theories and images amounts to a kind of disinformation. We are entering an era where a neural network could produce video of someone saying something they never said. And we, as a human, would be unable to tell the difference. ‘Fake news’ is the circulation of stories that can be experienced as if they are real, even when there is no corresponding thing the sign refers to in the ‘real world’, or outside of the simulation itself, and the algorithms used by Facebook and other platforms have no financial interest in telling the truth.

"Produced by a code or linguistic form that does not really refer but merely simulates reference, the simulacrum is the image or the reproduction that testifies to the short-circuiting of reference in postmodernism." (Simpson, Time, Technology, and the Conversations of Modernity.), p.138)

see virtual reality as the simulation of embodied presence.

sources and further reading: William Bogard, The Simulation of Surveillance.