Inductors

A inductor is an electrical component that stores energy in its magnetic field. Inductors are very simple components that are usually nothing more than a conductive material made into a coil in order to increase the magnetic field. When the current flowing through an inductor changes, creating a time-varying magnetic field inside the coil, a voltage is induced, which opposes the change in current that created it. Inductors are used in electronics where current and voltage change with time. Inductors are used to delay and reshape alternating currents.

Inductance is the property that materials have that causes current to be generated when a change occurs in the current flowing. This the result of magnetic field forming around a current-carrying conductor which tends to resist changes in the current. Electric current through the conductor creates a magnetic flux proportional to the current. A change in this current creates a corresponding change in magnetic flux which, in turn, by Faraday's law generates an electromotive force (EMF) that opposes this change in current.

Inductance is a measure of the amount of EMF generated per unit change in current. For example, an inductor with an inductance of 1 henry produces an EMF of 1 volt when the current through the inductor changes at the rate of 1 ampere per second. The number of loops, the size of each loop, and the material it is wrapped around all affect the inductance. For example, the magnetic flux linking these turns can be increased by coiling the conductor around a material with a high permeability such as iron.

- From Wikipedia

Types of Inductors:

Ideal inductors - these have inductance but no resistance or capacitance. Ideal inductors do not dissipate or radiate any sort of energy.

Real inductors -  these behave as resonant circuits because they are self-resonant.

Edit:

In an electrical circuit, resonance occurs at a particular frequency when the inductive reactance and the capacitive reactance are of equal magnitude, causing electrical energy to oscillate between the magnetic field of the inductor and the electric field of the capacitor.
Resonance occurs because the collapsing magnetic field of the inductor generates an electric current in its windings that charges the capacitor and the discharging capacitor provides an electric current that builds the magnetic field in the inductor, and the process is repeated. An analogy is a mechanical pendulum.
At resonance, the series impedance of the two elements is at a minimum and the parallel impedance is a maximum. Resonance is used for tuning and filtering, because resonance occurs at a particular frequency for given values of inductance and capacitance. Resonance can be detrimental to the operation of communications circuits by causing unwanted sustained and transient oscillations that may cause noise, signal distortion, and damage to circuit elements. - From Wikipedia