N-body simulations involve studying the dynamics of a system of interacting particles, typically in astrophysics and cosmology. These simulations track the motions of individual particles under gravitational forces, allowing researchers to understand the structure and evolution of complex systems such as galaxies, star clusters, and dark matter. N-body simulations are used to model a wide range of phenomena, from the formation of galaxies to the interactions between galaxies in a cluster. They are powerful tools for testing theories and making predictions about the behavior of dynamic systems in the universe.