This document defines simulation and discusses its uses and limitations. Simulation involves developing a model of a system and running experiments on that model to understand the system's behavior and evaluate changes. It is best used when testing potential changes is too complex, costly or disruptive for the real system. The key advantages are exploring "what if" scenarios without impacting operations and compressing or expanding time. Potential challenges include the expertise required and interpreting results. Simulation has wide applications in manufacturing, military, transportation and other domains.