Inductor is a device which is made by wounding coils over any material or simply air. They are similar to solenoid. It works on the basis of Faraday’s law of electromagnetic induction which states that on application of time varying magnetic field ( as it is a AC source) , a voltage is induced and voltage will oppose the cause that has created it. And hence a reverse current is developed which opposes the actual varying current. Thus inductors are used to limit the changing current. Ideal inductors have no resistance as well as no capacitance but in practical they have resistance of the wire from which they are made and capacitance due to varying electrical field between turns and is known as parasitic capacitance. In this type of capacitance the two turns of coil serves as two plates of capacitor. At low frequency it can be neglected but at high frequency this causes oscillations due to resonance and is harmful. The frequency at which these oscillations began is known as Self-resonant frequency (SRF).
Therefore at low frequencies parasitic capacitance can usually be ignored, but in high frequency circuits it is a major problem. At higher frequencies, resistance and resistive losses in inductors grow due to skin effect in the inductor's winding wires.