It's a measurement of the amount of electricity used, i.e., energy.
Multiply the power of an appliance in kilowatts by the length of time in hours its turned on for to calculate the number of kilowatts used.
If the power is given in watts, divide by 1000 to convert to kilowatts.
E.g. a 100 watt bulb for 200 hours uses 100/1000 x 200 = 20 kWh