A passive component that stores magnetic energy in electronic circuits and suppresses current changes. Composed of coiled conductors, used as noise filters in power circuits of manufacturing equipment, reactors in inverter control circuits, power smoothing circuits in NC machine tools, and choke coils in motor drive circuits. Available in ferrite core, iron powder core, and air core types, selected based on inductance value, rated current, and frequency characteristics. Unlike resistors and capacitors, this component utilizes inductive action through magnetic coupling and is essential for EMC countermeasures and power quality improvement.