The equation a² + b² = c² is known as the Pythagorean theorem. It describes the relationship between the lengths of the sides of a right triangle. In this equation, a and b represent the lengths of the two shorter sides, while c represents the length of the hypotenuse, the side opposite the right angle. This theorem is fundamental in geometry and is used in various fields, including architecture, engineering, and trigonometry. It helps in calculating distances and designing structures, ensuring they are stable and accurate.