BCS theory, named after physicists John Bardeen, Leon Cooper, and Robert Schrieffer, explains how certain materials become superconductors at low temperatures. It describes the formation of Cooper pairs, which are pairs of electrons that move through a lattice structure without resistance. This phenomenon occurs when attractive interactions between electrons overcome their natural repulsion. The theory highlights the importance of phonons, or lattice vibrations, in facilitating the pairing of electrons. As a result, BCS theory provides a framework for understanding superconductivity, helping scientists develop new materials and technologies that can operate with zero electrical resistance, which has significant implications for energy efficiency and advanced electronics.