What is the middle of the Earth called ?

THE MIDDLE OF THE EARTH IS KNOWN AS THE CORE.

Explanation: The core can be defined as the middle of the earth. It is composed mostly of iron, some nickel, and about 10- 15 percent of a less dense material, probably silicon, oxygen, or sulfur.

The temperature at the inner core's surface is estimated to be approximately 5700 K (5430 °C or 9806 °F), which is about the temperature at the surface of the Sun.