What is the difference between a kW and a kWh?

A kilowatt is a measure of power, and a kilowatt-hour is a measure of energy.

Power = Energy / Time

Power is the amount of energy required per second.

To better understand the concept
Just like speed is the amount of distance travelled divided by the time taken to do so, power is the amount of energy consummed divided by the time taken to do so.

Therefore, Energy is:

Energy = Power x Time

1 kWh = 1 kW x 1h. If you use a 1 kW appliance during 1 hour, you will have consumed 1 kilowatt-hour (1 kWh).

A computer consumes approximately 1 kW (1000 watts) of power. If you use it for 2 hours, the amount of energy used is:

1 kW x 2 h = 2 kWh.