THE INTERNAL STRUCTURE OF THE EARTH

Above is an illustration of the Earth's internal structure. You'll see the Earth's crust, mantle, outer and inner cores.

The crust is the Earth's covering. It has two different types - the thin oceanic crust and the thick continental crust. The thin oceanic crust are mostly made up of basalt, and underlies the ocean basins, while the thick continental crust is mostly made up of granite, and underlies the continents.

The Earth's mantle is its second layer, lying between the crust and the core. It is the biggest part of the Earth, and takes up 84% of its volume. The mantle is divided in two sections - the Asthenosphere and the Lithosphere. The Asthenosphere is found below the Lithosphere, and is made up of plastic-like fluid. The Lithosphere, on the other hand, is at the top part of the mantle, and is made up of cold, dense rock. The mantle has an average temperature of 3000 degrees Celsius. The lowest temperature of the mantle is beneath the crust, while the highest temperature is where the mantle is in contact with the core.

The core of the Earth is its source of heat. It is divided into the outer core and the inner core. The outer core is liquid because the temperatures found here can melt the iron and nickel alloy. The inner core is solid and has a temperature higher than the outer core.

The internal structure of the Earth can be compared to the cross-section of any fruit, such as this calamansi:

Its green outer layer represents the Earth's crust.

When you cut it in half, you'll see a very thin part of its skin, the seeds, and its yellow flesh. The yellow flesh represents the Earth's mantle, and the seeds its core. 

References:

http://gamediv1.weebly.com/mantle.html

http://geology.com/nsta/earth-internal-structure.shtml