But the quick (and very simplified) answer is: Reactance is the AC version of Resistance, which is primarily a DC measurement. Capacitive reactance, then, is the impedance to the flow of alterating current in a capacitor. Inductive reactance is the impedance to the flow of alterating current in an inductor.
Herein, what is inductance and reactance?
In electrical and electronic systems, reactance is the opposition of a circuit element to a change in current or voltage, due to that element's inductance or capacitance. As frequency goes up, inductive reactance also goes up and capacitive reactance goes down.
What do you mean by inductive reactance?
Inductive reactance is the name given to the opposition to a changing current flow. This impedance is measured in ohms, just like resistance. In inductors, voltage leads current by 90 degrees.