What is entropy?

You ask: What entropy?

Caveman stack rocks in neat pile. Wind, time, bump — pile always fall to mess, never mess jump back to pile. Why? Only few ways to be neat, but many many ways to be messy — just ten rocks can jumble more than three million different ways. So chance push everything toward mess. That mess-count called entropy. Hot fire always spread heat to cold air, never cold gather heat back to fire — heat spread because spread got more ways to happen. Drop berry juice in water: it mix through, never un-mix on own. Whole world slowly slide from tidy to spread-out. Caveman can tidy one pile, but Caveman burn food and sweat to do it — Caveman push mess somewhere else. Cave wisdom: everything drift to mess, because mess got more roads than neat.