Simulations are computer models that represent real or imaginary systems. They come in different categories like physical, process, situational, and procedural simulations. Simulations provide an interactive learning experience for students and allow them to manipulate variables. They have advantages like student involvement, safety, and practice without real-world risks. However, simulations also have limitations such as time demands and difficulty intervening directly. Effective use of simulations requires careful preparation, debriefing with students, and encouraging group work.