A Residual-Current Device (RCD) is a safety device used in electrical installations to prevent electric shock and reduce the risk of electrical fires. It works by monitoring the flow of electricity through a circuit and detecting any imbalance between the live and neutral wires. If it senses a difference, indicating a potential leak of current, the RCD quickly disconnects the power supply. RCDs are commonly used in homes and workplaces, often installed in circuit breakers or as standalone units. They are essential for protecting people from electric shocks, especially in areas where water is present, such as bathrooms and kitchens, making them a crucial component of electrical safety.