The three power parameters active power (P), apparent power (S) and reactive power (Q) are mathematically related to each other via the power factor, and also via the geometric addition of the various power parameters.
The reactive power is the power which is present at a pure reactance, an inductance or capacitance. In reactive power, the applied voltage has a phase shift of 90 degrees with respect to the current flowing through the reactance. If the current is in phase with the applied voltage, it is an active power; if it has a phase shift of more than zero degrees and less than ninety degrees with respect to the voltage, it is an apparent power.
When apparent power is expressed in volt-amperes( VA), reactive power is expressed as Voltage-Ampere Reactive( VAR) to distinguish it. One Var corresponds to one ampere (A) multiplied by one volt (V).