The final choice of lunar orbit rendezvous changed the CSM's role to the translunar ferry used to transport the crew, along with a new spacecraft, the Lunar Excursion Module (LEM, later shortened to LM (Lunar Module) but still pronounced ) which would take two individuals to the lunar surface and return them to the CSM.
The choice of lunar orbit rendezvous shifted the role of the Command Service Module (CSM) from its original purpose to that of a transport vehicle for crew members and a new spacecraft, the Lunar Excursion Module (LEM), which would land on the moon and bring astronauts back to the CSM.