Inductors

Inductors, also called coils or chokes, are electronic components made out of a coil of wire that is wound around a magnetic core. 

They are used for choking, blocking, attenuating, or filtering/smoothing high frequency noise in electrical circuits.

They are also used for storing and transferring energy in power converters (dc-dc or ac-dc).

Lastly they are used to tune oscillators or LCs (inductors / capacitors) and also in circuit impedance matching.  

The basic types of inductors include Air Core Inductors, Iron Core Inductors, Ferrite Core Inductors and Iron Powder Inductors.