Simulations are representations of reality that model crucial characteristics of a real situation without risk. They involve human decision-making within an operational model that abstracts and scales up a larger system. Effective simulations contain these three elements: a basic operating model, human activity, and a scaled representation of reality. Simulations provide motivation for learning, allow mistakes without major risks, and offer practice in real-life situations. Teachers should consider content, quality, usability, and age-appropriateness when using simulations, and implement them for uninterested students or those needing extra practice.