Einstein's field equations are a set of ten interrelated equations in general relativity that describe how matter and energy influence the curvature of spacetime. Formulated by Albert Einstein in 1915, these equations show that massive objects like planets and stars warp the fabric of spacetime around them, leading to the phenomenon we perceive as gravity. The equations relate the geometry of spacetime, represented by the Einstein tensor, to the energy and momentum of whatever matter is present, represented by the stress-energy tensor. This relationship helps explain various cosmic phenomena, including the bending of light around massive objects and the expansion of the universe.