Here's a breakdown:

* Crust: The outermost layer, thin and rocky, what we walk on.

* Mantle: A thick layer of mostly solid rock, but behaves like a very viscous fluid over long periods. It's responsible for plate tectonics.

* Outer Core: Liquid iron and nickel.

* Inner Core: Solid iron and nickel, incredibly dense and hot.

Let me know if you'd like to know more about any of these layers!