Basically, that whatever you do now will affect everything else in a geometric fashion. Take the following example which my history teacher presented to his class:

You're driving home after a day at work, or school, or whatever. You're a good driver, you obey the speed limit and are careful. Unfortunately, you hit and kill a small puppy. You get out of your car and witness the dog corpse and while you are evaluating your grief, you see the owner, a small innocent boy running down the driveway. His face slowly melts from a general joy and innocence to horror and shock. Maybe, because of this one moment, his whole life is altered. What could've become another Ghandi may now destined to be the next Hitler. And, its all your fault.

Its very similar to the butterfly in Africa example, but that's a whole other node. Something to think about when you do a hit and run on the neighbor's pet rabbit.