Reactive power in AC circuit
Capacitors and Inductors are Reactors and account for the reactive power in an AC circuit.  When you measure the current and voltage in an AC circuit, you measure what is called Apparent Power, which will appear to be greater than the actual True Power being used in the circuit if the circuit has reactors in it.  They store and release energy, causing current to flow in the process even though the Reactive Power isn't being used and contributing to the &quot;Power&quot; you &quot;see&quot;.  To recognise the difference between the energy being stored and being used, we refer to True Power in W(watts), Reactive Power in VAR (volt-amps reactive) and Apparent Power in VA (volt-amps).
The Apparent Power is not simply the sum of the True Power and the Reactive Power.  Instead it's a Pythagorean relationship where the Apparent power is the long side of a square triangle, the True Power is the horizontal line and the Reactive Power is the vertical line.  You can apply trigonometric rules and the Pythagorean Theorem to calculate values on different sides of the triangle from your known values.