Formation of Earth and Moon
The sun ignited during the T-Tauri phase and this blew away most of the protoplanetary disk, leaving chunks, boulders and planetesimals. Some of the larger, more stable bodies remained in a well spaced orbit around the Sun, Earth being the 3rd body from the Sun. At one point, another planetesimal collided with Earth. The force of this massive collision shattered the rock mantle into many pieces and sprayed some of them into space. Some of this material collected together, forming a second planet orbiting earth, called the moon.