The kind of rock found on the moon that is made up of older rocks stuck together is called a breccia.

Breccias are formed when fragments of existing rocks are broken, transported, and then cemented together by a mineral matrix. On the Moon, this process happens due to impacts from meteoroids and asteroids. The intense force of these impacts shatters existing lunar rocks, and the fragments are then re-welded together by the heat and pressure generated.

So, breccias are essentially "rock conglomerates" from the Moon's history, offering valuable insights into the geological processes that have shaped its surface.