Dive into the rabbit-hole on Wikipedia.
Commonly known as the 80-20 rule. It describes the phenomenon that a larger amount of consequences (typically 80%) come from a smaller part of causes (typically 20%). For example, you’ll cook 20% of the meals you know 80% of the time. I like to think of this as a rule of inequality, as it highlights often vastly asymmetrical relationships that appear in climate change, social phenomena, economics, and pretty much anywhere else you look. A fraction of corporations are responsible for the majority of CO2-emissions or deforestation. A few thousand billionaires have as much wealth as a couple hundred million people.