Question

What is geothermal power

Answer 1

Look at the parts of the word ... you've seen them both before:

"Geo ..." . . . has something to do with the Earth.

"... thermal" . . . has something to do with heat.

"Geothermal" . . . "Earth heat".

You know that the Earth's core is liquid metals, at high temperature.
You may also know that when people go down into a deep mine, it's
always warm down there.

Some of the heat from the Earth's core soaks up through the Earth,
and there's actually a lot of it available without going too deep below
the surface.

You may have read about "hot springs" ... pools of water that are always
hot, because they extend down deep and get heated by the Earth's heat. 
And you may have seen pictures or videos of "geysers" ... deep holes in
rock where there's water down at the bottom, which gets heated by the
Earth's heat, and when it gets to boiling temperature, this stream of hot
water and steam comes shooting up out of the hole.  There are a lot of
those geysers in Yellowstone National Park in Wyoming.

Well, if there's enough of this hot water close enough to the surface,
then you can actually install pipes to bring it up to the surface, use the
hot water to heat houses and buildings, and even use the steam to spin
turbines and generate electric power !  Then you're using "Geothermal"
energy . . . "Earth heat".

The country of Iceland is almost completely based on geothermal
energy.

Answer 2

Geothermal electricity is electricity generated by geothermal energy