A circuit breaker is an electrical device designed to protect an electrical circuit from damage caused by overload or short circuit. It automatically interrupts the flow of electricity when it detects a fault, preventing potential hazards like fires or equipment damage. Circuit breakers come in various types, including miniature circuit breakers (MCBs) and residual current devices (RCDs), each serving specific functions. They are commonly used in homes and industries to ensure safety and reliability in electrical systems, allowing for easy reset after a fault is cleared.