Question

What is difference between kilowatt and kilowatt hour?

Answer 1

Kilowatt hour is a measure of ENERGY
Kilowatt is a measure of POWER

Answer 2

Those two units can be compared to a 'mile per hour' and a 'mile per hour - hour'.
One is a rate.  The other is a quantity, after maintaining a rate for some time.

-- 'Joule' is a unit of energy.  It's the amount of work (energy) you do
when you push with a force of 1 newton though a distance of 1 meter.
Lifting 10 pound of beans 3 feet off the floor takes about 40.7 joules of energy.

-- 'Watt' is a rate of using energy . . . 1 joule per second.
If you lift 10 pounds 3 feet off the floor in 1 second, your power is 40.7 watts.

-- 'Watt-second' is the amount of energy used in one second,
at the rate of 1 joule per second . . . 1 joule.

-- 'Watt-hour' is the amount of energy used in one hour,
at the rate of 1 joule per second . . . 3,600 joules.

-- 'Kilowatt' is a bigger rate of using energy . . . 1,000 joules per second.

-- 'Kilowatt - second' is the amount of energy used in one second,
at the rate of 1,000 joules per second . . . 1,000 joules .

-- 'Kilowatt - hour' is the amount of energy used in one hour,
at the rate of 1,000 joules per second . . . 3,600,000 joules .

Depending on where you live, 3,600,000 joules of energy bought
from the electric company costs something between 5¢ and 25¢.