A study of many physical phenomena like the weather, stellar motion, even water falling from a faucet has revealed results that are totally random and impossible to predict. The unpredictability has been termed as the Chaos Theory.
An important conclusion from studies with the Chaos theory is that even a small, insignificant change in the initial conditions can create large changes in the final outcomes. This is due to the fact that at every stage the results change in a exponential manner depending on the conditions prevailing in the previous stage.
The Butterfly Effect is an exotic term coined to describe the effect of the unpredictability of the Chaos theory. Even an insignificant event like a butterfly flapping its wings in a forest in one corner of the Earth can be the reason behind a tornado occurring on the other side of the planet.