Concepts of the butterfly effect and Chaos Theory??

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from what i know the the butterfly effect says that "an event as small as a butterfly flapping its wings can cause a much huger effect such as a hurricane half way across the earth".... and that the butterfly effect is a part of the chaos theory.... thats all good n nice.... bt what i want to know is wat exactly is the chaos theory... what does it say?? what does it signify??