There are two main parts of the Earth's core: the liquid outer core and the solid inner core.
The outer liquid has a depth of 2890 to 5000km from the surface of the Earth. It makes up 30.8% of Earth's mass. Its temperature is around 3700 degrees Celcius.
Convection currents in the outer core mixed with the Earth's rotation help maintain the Earth's magnetic field. This magnetic field protects life on Earth from the Sun's deadly radiation.
The inner core is about 5,150-6,370km deep. The inner core makes up only 1.7% of the Earth's mass. It is a solid iron ball that is unattached from the molten outer core. The inner core has a temperature similar to the surface of the Sun, or around 5500 degrees Celsius.