Albert Einstein is known for his theory of relativity, which revolutionized the understanding of space, time, and gravity. Introduced in the early 20th century, the theory consists of two parts: special relativity and general relativity. Special relativity, published in 1905, introduced the groundbreaking concept that the laws of physics are the same for all observers, regardless of their relative motion, and established the famous equation E=mc². General relativity, published in 1915, expanded these ideas to include gravity, proposing that massive objects curve spacetime, affecting the motion of other objects. Einstein’s work has profoundly influenced modern physics.