The thin outermost layer of the earth is the crust.  It is made of igneous, sedimentary, and metamorphic rocks. 
The continental crust is about 32 km think.  It is made of two layers.  The top layer is a light colored granite and the bottom layer is a more dense basalt rock.

The oceanic crust is less than 10 km thick.  The basalt extends beyond the continents to form oceanic crust.

The crust is broken into large sections called lithospheric plates.  There are seven major plates that drift on the hot, molten upper layer of the mantle.

The middle layer of the earth is known as the mantle.  It is about 2900km thick.  It is mainly consists of silicon, oxygen, iron and magnesium. 
Is most of the mantle the material can flow like a thick liquid because of the high temperature and pressure.

The upper layer of the mantle is partially melted rock. It is called the asthenosphere.  When a volcano erupts, the magma from the top of the mantle reaches the surface as lave.

The earth's core is about 3900 km below the surface of the planet.  The core has a radius of 3550 km.  It is believed to be made of iron and nickel which are very dense metals. 

The temperature in the core is a tremendous 5000C.  Normally iron and nickel would be melted at this great temperature but the enormous pressure pushes them together to make them solids.  This dense iron and nickel are thought to be the cause of the earth's magnetic fields.