An application that simulates real-world activities using mathematics. Real-world objects are turned into mathematical models and their actions are simulated by executing the formulas.

For example, some of an airplane's flight characteristics can be simulated in the computer. Rivers, lakes and mountains can be simulated. Virtually any objects with known characteristics can be modeled and simulated.

Simulations use enormous calculations and often require supercomputer speed. As personal computers became more powerful, more laboratory experiments have been converted into computer models that can be interactively examined by students without the risk and cost of the actual experiments.