There are 4 different types of layer on the Earth. There is the Earths crust, earths mantel, inner core, and outer core.
Earths Crust: Surprisingly this is not what we walk on. The crust is composed of igneous, metamorphic, and sedimentary rock. The temperature increases the farther you go.
Mantle: The mantle is under the crust. It is also 2900 km. deep. It is separated into an upper and lower mantle. Although it is largely hidden, we can still see cracks, letting the molten rock escape. The cracks they find are volcanos.
Outer Core: Deep into the Earth there is the outer core. It is measured to be 6800 km. across. The outer core s about twice as big as the moon.
Inner Core: The inner core is about 2440 km. across. This is the deepest part of the Earth. It contains iron, the iron in the inner core is not pure. The inner core is extremely hot! It can be 9000-13000 degrees.