What parasitic characteristic creates an inductor’s self-resonance?

An inductor is typically created by winding a wire into a coil. Because each turn of the wire is a separate conductor running parallel to adjacent turns and separated by an insulator (like an enamel coating or air), tiny parasitic capacitors are formed between the windings. This unintended capacitance is known as inter-turn capacitance. In any electrical circuit where both inductance (the coil itself) and capacitance (the parasitic effect between the turns) are present, the component will naturally have a resonant frequency. At one specific high frequency, this inter-turn capacitance will resonate with the inductor's own inductance, causing the component to self-resonate. Above this frequency, the inductor will actually exhibit capacitive reactance and stop behaving like a normal inductor.