IDT Energy World

A watt is the rate of electricity an appliance uses at any particular moment.  A watt-hour is the total amount of energy that has been used over an amount of time, such as an hour. Let’s say you have a laptop computer which uses 50 watts. At the end of one hour the laptop will have used 50 Watt-hours. Which is the same as 0.050 kilowatt-hours (kWh.)
It is similar to saying that a car, at this moment, is going 50 mph. If it continues to travel at that speed for one hour, then it will have gone 50 miles by the end of the hour. In this example we are using distance to compare to amount of energy used.