The US National Aeronautics and Space Administration (NASA) had drawn up a 3-stage plan for the Moon landing:
* A spacecraft would be put into Earth orbit.
* The spacecraft would then fire rockets to take it out of Earth orbit, and toward the moon.
* When it reached the moon it would not land directly but would go into orbit. A special landing craft would separate from the orbiting spacecraft to descend to the surface of the moon.
The return from the Moon’s surface also involved 3 stages.
* Take off from the Moon in the ascent module of the landing craft.
* Rendezvous with the orbiting spacecraft, and transfer of the crew from ascent module to mother ship
* Return of the spaceship from Moon orbit to Earth, return to Earth atmosphere, and splashdown in the sea.
The problems of rendezvous and docking in space had been ironed out during the Gemini missions. At the time these maneuvers were being practised a huge rocket capable of catapulting a spacecraft to the Moon was being readied. This was the Saturn V rocket.
Saturn V was a three-stage rocket which weighed about 2700 tonnes at take-off.