What is a geothermal?

I'm looking at a book on yellow stone park, and there is a beautiful picture of Morning Glory Pool. It says it's a geothermal, what does that mean? Heated water?

What is a geothermal?
I'm just furthering the previous answer. In case you need more information, geothermal heating relates to the internal heat of the Earth.
Reply:yes it is heated water, it is heated by the magma beneath the surface of the caldera that yellow stone sits on top of. a caldera is what is left over when a volcano exploded leaving only the rearmament of a volcano
Reply:Correct! Geothermal is heated water coming from underneath the earth caused by coming in contact with hot rocks in the vicinity of volcanoes or hot springs.
Reply:Basically it means it is a heated geological feature. In this case it is not constricted enough to by a geyser, but is a hot spring pool hot enough to broil yourself in.