As our solar system was forming nearly four and a half billion years ago, a planet-sized object struck the early Earth, leading to the formation of the moon, possibly from a hot, spinning cloud of rock vapor called a synestia. But after the Earth and moon had condensed from the vapor, there was another phase of growth as meteorites crashed into both bodies.
Source:
https://phys.org/news/2019-07-early-meteorite-impacts-moon.html