Here's a breakdown:

* Lithosphere: The rigid outermost layer of Earth, composed of the crust and the uppermost part of the mantle.

* Asthenosphere: A semi-molten, partially solid layer beneath the lithosphere. It's more fluid than the lithosphere and allows the tectonic plates to move.

Think of it like a giant, slow-moving "slush" with the rigid lithospheric plates floating on top. The movement of the asthenosphere drives plate tectonics.