The formation of the Moon is still a subject of scientific investigation and there are several theories that have been proposed to explain its origin. The most widely accepted theory is known as the Giant Impact Hypothesis, which suggests that the Moon formed as a result of a collision between a Mars-sized protoplanet called Theia and the early Earth.
According to this theory, about 4.5 billion years ago, during the early stages of the Solar System's formation, a Mars-sized object, Theia, collided with the young Earth. The impact was so powerful that it caused a significant portion of the Earth's mantle and some of Theia's material to be ejected into space. This ejected material eventually coalesced to form the Moon.
The collision would have been an incredibly violent event, causing widespread melting and vaporization of rock. Over time, the debris from the impact would have formed a disk of molten material around the Earth, called a protolunar disk. Through the process of accretion, the debris in this disk gradually came together to form the Moon.
The Moon's formation was a complex process that involved multiple stages, including the initial impact, the formation of the protolunar disk, and the subsequent accretion of material to form the Moon. The exact details of these processes are still the subject of ongoing research, and scientists continue to study Moon rocks and conduct simulations to refine our understanding of its origin.