Simulation is a complex social endeavor, in which human beings interact with each other, a simulator, and other technical devices. The goal-oriented use for education, training, and research depends on an improved conceptual clarity about simulation realism and related terms. The article introduces concepts into medical simulation that help to clarify potential problems during simulation and foster its goal-oriented use. The three modes of thinking about reality by Uwe Laucken help in differentiating different aspects of simulation realism (physical, semantical, phenomenal). Erving Goffman's concepts of primary frames and modulations allow for analyzing relationships between clinical cases and simulation scenarios. The as-if concept by Hans Vaihinger further qualifies the differences between both clinical and simulators settings and what is important when helping participants engage in simulation. These concepts help to take the social character of simulation into account when designing and conducting scenarios. The concepts allow for improved matching of simulation realism with desired outcomes. It is not uniformly the case that more (physical) realism means better attainment of educational goals. Although the article concentrates on mannequin-based simulations that try to recreate clinical cases to address issues of crisis resource management, the concepts also apply or can be adapted to other forms of immersive or simulation techniques.