How Inductor works

When a current flows into an inductor, it doesn't go round and round and round the turns, taking its time to get to the other end. An inductor wound with 100 feet of wire behaves nothing like a 100 foot wire. Why?

It's because when the current begins flowing, it creates a magnetic field. This field couples to, or links with, the other turns. The portion of the field from one turn that links with the others is the measurable quantity called the coefficient of coupling. For a good HF toroid, it's commonly 99% or better; solenoids are lower, and vary with aspect ratio. The field from the input turn creates a voltage all along the wire in the other turns which, in turn, produce an output current (presuming there's a load to sustain current flow). Consequently, the current at the input appears nearly instantaneously at the output. Those who are physics oriented can have lots of fun, I'm sure, debating just how long it takes. The field travels at near the speed of light, but the ability of the current to change rapidly is limited by other factors.The coupling of fields from turn to turn or region to region is what brings about the property of inductance in the first place.
One of the characteristics that make inductors useful is that their reactance (opposition to AC current) increases with frequency. (unlike a capacitor, for which the reactance decreases with frequency).

Thus inductors when combined with capacitors become useful when you want to make filters that let only chosen frequencies through, such as cross-overs for speakers or tuner circuits in radios.

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