What is the Butterfly Effect-?

The phrase relates to chaos theory. It's one of those coined sound bites that reporters love because it sounds good, while not really contributing much accurate information (like "the information superhighway" being used to describe the internet). The more accurate name is "sensitive dependence on initial conditions". I can't remember the exact countries that the original example used, but the idea is that a storm could be caused off the coast of country xxx by something as small as a butterfly flapping its wings over country yyy weeks earlier, due to the unpredictability (i.e. chaos) and large number of variables involved in a planet's weather. An alternative way of looking at it is to imagine 2 planets with perfectly identical weather systems at a single moment. If you then introduced a butterfly for a single wingflap into just one of the planet's weather systems, this planet could experience a storm over country xxx a few weeks later as a result, where the other planet might not. That's where the "sensitive dependence on initial conditions" comes in.... :o)

In addition:The butterfly effect is simply:

If a butterfly flaps its wings in china, would it have an effect on the weather patterns in London? The obvious answer is no. But since every action has an effect on other probabilities... The result is infinite.

It is also a good movie.