The document discusses Pareto's Principle, also known as the 80/20 rule, which states that roughly 20% of inputs (such as causes or efforts) account for 80% of the outputs (such as consequences or results). Some examples mentioned include 20% of people owning 80% of wealth, 20% of defects causing 80% of problems, and 20% of work accounting for 80% of results. The principle can be applied to many areas such as productivity, quality control, revenue, and more.