Kilowatts is like the rate at which propane is flowing out of your tank. Kilowatt-hours is like the total amount of propane you use in an hour.

Of course instead of propane, its electrical energy.

In heating language its called BTUs and BTU per hour. You buy natural gas on your heating bill in units of 100,000 BTUs, these are called a 'Therm'. The rate at which your furnace can heat your house is measured in BTU per hour.

Watts are like BTU per hour (rate of energy transfer) Watt-hours are like BTU (total energy)

kW is a thousand watts (rate of energy transfer) KWH is a thousand watts for one hour (total energy)