Simon Sinek's "Start With Why" emphasizes the importance of defining and communicating one's core purpose ("WHY") before focusing on "HOW" and "WHAT." The book uses a "Golden Circle" model to illustrate this, arguing that inspirational leaders prioritize their purpose to build trust and loyalty. Sinek provides real-world examples like Apple and the Wright Brothers to demonstrate this principle, stressing authenticity and the ongoing need to reaffirm one's "WHY" for sustained success. The ultimate message advocates for purpose-driven leadership to inspire lasting impact, rather than solely focusing on short-term gains.