A definition of computer simulations is given, emphasizing the dynamic aspects of simulations. The important role of visualization in many simulations is explained. Computational issues in simulations are connected to observational issues with instruments via the microscope metaphor. Digital simulations are compared with analog simulations, and the advantages and disadvantages of simulations are explored. Agent-based simulations are compared to equation-based simulations.
Keywords: agent-based simulations, analog simulations, computer simulations, digital simulations, equation-based simulations, visualization