I didn’t really have a “plan” for this. I just liked how creatively books used it and it’s a fascinating subject.
Wikipedia defines the butterfly effect as “the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state.” Basically, the butterfly effect is when you do something somewhere or sometime, and the consequences of your actions get larger and larger, until something big happens.
In “A Sound of Thunder” a tiny action, stepping in mud, causes a change in which a different president is elected. Everything is fictional, including the presidents, but it shows a great example of the effect.
If you, hypothetically, went fishing, and fished all the fish in a creek, then you might have doomed humanity in the future. Perhaps a bunch of animals relying on that animal for food die, and omnivores who eat that animal for food turn to eat oxygen producing plants or something. That is the example of the butterfly effect.
Many books involving time traveling take use of the butterfly effect. In my opinion, it is a cool concept.