Error. Within the field of computer graphics, the term "artefact" refers to an error or anomaly that has occurred in the synthesis of an image. The use of this term comes from its broader meaning as "a feature not naturally present, introduced during preparation or investigation". Computer graphic artefacts are often a side effect of the algorithm used to construct a synthetic image. Artefacts could be glitches in sound, patterns that appear when an image is transformed, or the unnatural appearance of objects in a virtual world.

Simulation. Models for simulating reality predate written language as tools used for learning or understanding. Typically, these simulations use symbols and rules to model a particular aspect of the real world. Toys, games, maps, symbolic languages, game theory, and artificial life all represent different methods for modelling reality. More recently these reality models have become so ubiquitous that we are constantly shifting from the real to the hyperreal, often accepting simulacra as reality. Our models of reality are either attaining a level of complexity where they become equal to the reality, or our perception is shifting to accept the simulation, allowing our mind to fill in the detail.