why those rocks on moon helps scientists to know the monns origin, compsition?

Answer 1

By studying the physical and chemical properties of rocks on the moon scientists can tell about how and when the moon was formed and what kind of minerals exist on the moon which can be mined and used later.

Answer 2

It's all made of the same stuff. Just like all of the rock layers in the earth's crust tells scientists what kind of animals lived in what time period. It's the same concept.