Modeling and Simulation
Modeling and Simulation is a discipline for developing a level of understanding of the interaction of the parts of a system, and of the system as a whole. The level of understanding which may be developed via this discipline is seldom achievable via any other discipline.

Modeling and simulation (M&S) is the use of models, including emulators, prototypes, simulators, and stimulators, either statically or over time, to develop data as a basis for making managerial or technical decisions. The terms “modeling” and “simulation” are often used interchangeably.
Although the terms “modeling” and “simulation” are often used as synonyms within disciplines applying M&S exclusively as a tool, within the discipline of M&S both are treated as individual and equally important concepts. Modeling is understood is the purposeful abstraction of reality, resulting in the formal specification of a conceptualization and underlying assumptions and constraints. M&S is in particular interested in models that are used to support the implementation of an executable version on a computer. The execution of a model over time is understood as the simulation.

Complicated model is usually crated using super computer.

Examples of where it can be used.
-better preparedness in the event of a nuclear explosion
-Global Climate Change
-supporting deep water operation of the US Navy
-simulating the surface of neighbored planets in preparation of NASA missions
-forecasting

sources
^ http://celebrating200years.noaa.gov/breakthroughs/climate_model/welcome.html
^ “New models to aid hurricane-evacuation planning – fox59.com.” Latest breaking news, daily news, local news & current events articles from FOX59, Indianapolis