kW, short for kilowatt, is 1,000 watts. It is a measure of power or the rate at which electricity flows. So, the more watts an appliance needs to operate, the more electricity it will use. For example, a 100 W light bulb will shine brighter than a 20 W option, but more electricity is required to run it.
kWh, or kilowatt hour, refers to the energy an appliance uses in kilowatts per hour measured by kW x time. If you run the 100 W light bulb for one hour, you will use 0.1 kWh. If you run a 1 kW washing machine for one hour, you will use 1 kWh, and if you run it for two hours, you will use 2 kWh of energy.