Pickup
A pickup is an electronic device consisting of a metallic wire wound around magnets. It is used in electric guitars to convert the motion of steel strings into an electrical signal, that is then sent to an amplifier to be converted into sound.
Single coil pickups have a clear, bell-like sound, but are plagued by problems with interference and 60 cycle hum. Guitars known for using single coils include the Fender Stratocaster and Telecaster.
Humbucker pickups consist of two single coils wound in a way that they cancel out hum, and have their own unique sound which is a little heavier on average than single coils. Guitars known for humbuckers include the Gibson Les Paul and the Gretsch White Falcon.