Einstein's theory of general relativity is a scientific theory that explains how gravity works. Proposed by Albert Einstein in 1915, it describes gravity not as a force, but as a curvature of space and time caused by mass. This means that massive objects, like planets and stars, bend the fabric of space-time around them, influencing the movement of other objects. The theory has been confirmed through various experiments and observations, such as the bending of light around massive objects and the precise orbits of planets. It has become a fundamental part of modern physics, helping to explain phenomena like black holes and the expansion of the universe.