Relativity, formulated by Albert Einstein, revolutionized our understanding of space, time, and gravity, demonstrating that the laws of physics are the same for all observers and that the speed of light is constant regardless of the observer's motion. It consists of two theories: Special Relativity, which addresses the physics of objects moving at constant speeds, and General Relativity, which extends these principles to include acceleration and gravity, describing gravity as the curvature of spacetime caused by mass.