A PIR sensor, or Passive Infrared Sensor, is an electronic device that detects motion by measuring changes in infrared radiation. It is commonly used in security systems, automatic lighting, and energy-saving applications. The sensor works by identifying the heat emitted by objects, such as humans or animals, within its field of view. When a warm body moves across the sensor's detection zone, it triggers a response, such as turning on a light or sounding an alarm. PIR sensors are popular due to their low power consumption, reliability, and ability to cover a wide area, making them ideal for various applications in homes and businesses.