Simulation studies are fundamental to psychometric discourse and play a crucial role in operational and academic research. Yet, resources for psychometricians interested in conducting simulations are scarce. This Instructional Topics in Educational Measurement Series (ITEMS) module is meant to address this deficiency by providing a comprehensive introduction to the topic of simulation that can be easily understood by measurement specialists at all levels of training and experience. Specifically, this module describes the vocabulary used in simulations, reviews their applications in recent literature, and recommends specific guidelines for designing simulation studies and presenting results. Additionally, an example (including computer code in R) is given to demonstrate how common aspects of simulation studies can be implemented in practice and to provide a template to help users build their own simulation.