When you are doing a project or working towards a goal you make a lot of decisions (inputs) towards the goal. The 80-20 rule states that 20 percent of your inputs result in 80% of the outputs. If someone was doing an e-commerce business, 20% percent of their products result in 80% of the income. This rule is great for prioritizing the actions that give you 80% of your output rather than the other inputs that barely do anything for the output. Like trying to persuade a group of people to buy your product again when these groups of people weren’t even contributing 4% to your business revenue.