The best statement providing evidence that a scientific law is a description while a scientific theory is an explanation is:
"Laws of motion state that for any action force, there is an equal and opposite reaction force, while theories state that contact forces are due to electrostatic forces between the charged particles that make up matter."
This statement clearly distinguishes between the descriptive nature of a law (which provides a straightforward rule about how forces behave) and the explanatory nature of a theory (which seeks to explain the underlying reasons for phenomena).