Here's a breakdown:

* Asthenosphere: This is a semi-solid, partially molten layer within the upper mantle. It's known for its relatively low viscosity, allowing for slow, ductile deformation.

* Lithosphere: This is the rigid outermost layer of Earth, including the crust and the uppermost part of the mantle. It's broken into tectonic plates that move on top of the asthenosphere.

Think of it like this: Imagine a pot of boiling water with a thin layer of ice forming on the surface. The ice represents the lithosphere, and the boiling water represents the asthenosphere. The ice floats on the water, just as the tectonic plates float on the asthenosphere.