In the two theories namely, Giant impact hypothesis and Fission theory, the moon is said to be formed either from a part of earth or moon is formed due to the some geo or astro physical process taking place on earth.
In the Fission theory , it was stated by George Darwin that plant earth was spinning at a very fast rate and due to that a small part of earth got separated and it became the present day moon.
Like wise in the great impact hypothesis, it was stated that “Theia” the mother of moon goddess Selene hit the Earth and due to this impact a portion of the planet came off and eventually became the moon