A motion detector is an electronic device that senses movement in a specific area. It typically uses technologies such as passive infrared (PIR), ultrasonic, or microwave to detect changes in the environment. When motion is detected, the device can trigger alarms, lights, or other security systems, making it useful for home security and automation. These devices are commonly used in residential and commercial settings to enhance safety and energy efficiency. For example, in a home, a motion detector can turn on lights when someone enters a room, while in security systems, it can alert homeowners or authorities to unauthorized movement.