Motion detectors are devices that sense movement in a specific area. They are commonly used in security systems to detect intruders or in automatic lighting systems to turn on lights when someone enters a room. These detectors work by using various technologies, such as infrared sensors or microwave signals, to identify changes in the environment. When a person or object moves within the detection range, the motion detector sends a signal to trigger an alarm or activate a light. This technology is not only useful for security but also helps save energy by ensuring lights are only on when needed, making it a smart choice for homes and businesses alike.