Final answer:
The asthenosphere is a partially molten upper mantle layer that can flow and is located between the lithosphere and lower mantle. It facilitates the movement of tectonic plates.
Step-by-step explanation:
The asthenosphere is the partially molten upper mantle material that behaves plastically and can flow, located between the lithosphere and lower mantle. It is composed of warmer, more ductile rock that allows for the movement of tectonic plates. It is important to note that while the lithosphere is rigid and brittle, the asthenosphere is capable of deforming and flowing over long periods of time.