Computer simulation (alternately computer modeling) is the study and practice of creating models of actual processes on the computer. Computer simulation can be used in biology, physics, economics, chemistry, engineering, and other scientific fields: it is often more economical, faster, or otherwise preferable to study a simulation of a process of interest, rather than studying the process itself. For instance, in population modeling, it is much easier to simulate the interaction of predator and prey using a computer than actually studying predators and their prey in the wild.
Computer simulation has provided great leaps in our understanding of nature. Using simulations, we can study cell interaction, evolution, ecosystems, and plant growth. Currently, however, we lack the processing power and understanding of nature to do large-scale cell-level computations, so our simulations lack realism.
Physics is often only practical using intricate modeling, for instance of light diffusion over long distance. Using computer simulations, we can examine the energy pattern at long distances from lasers. We can also examine the results of collisions, explosions, &c at the atomic level, giving us greater understanding and more certainty of atomic-level processes.