MOSFET, or Metal-Oxide-Semiconductor Field-Effect Transistor, is a type of transistor that is widely used in electronic circuits. It is a three-terminal device that can be used as a switch or an amplifier. MOSFETs are popular because of their high input impedance, low power consumption, and high switching speed. They are commonly found in power supplies, motor control circuits, audio amplifiers, and many other applications. The development of MOSFETs has played a key role in the advancement of modern electronics.