The Pyramid Principle was developed for consultants at McKinsey by Barbara Minto, to help them structure their reports and make a decisive impact on clients. It is now widely part of the toolkit every strategy consultants around the world needs to learn and use.
The Pyramid principle is a hierarchical structure to create a logic and data-supported storyline. It should be prepared in advance. To make it short, your presentation needs to start with an introduction that states both the issue and your answer, and the rest of the presentation is here to support your answer.
That key message is supported by a combination of supporting arguments that, together, create a logical storyline naturally leading to conclude that your key message is true. Each supporting argument is made irrefutable with the help of supporting data.