1. Crust: This is the outermost, thin, and rocky layer. It is divided into oceanic crust (thinner and denser) and continental crust (thicker and less dense).

2. Mantle: This is the thickest layer, made up of hot, dense rock that flows slowly over time. It's divided into the upper mantle and the lower mantle.

3. Core: This is the innermost layer and is made up of two parts: the outer core (liquid iron and nickel) and the inner core (solid iron and nickel).