What was the command module Columbia in the Apollo 11?

The command module Columbia was the spacecraft used in NASA's Apollo 11 mission, which marked the first manned moon landing in July 1969. It housed the astronauts—Neil Armstrong, Buzz Aldrin, and Michael Collins—and served as their living quarters and control center during the mission. Columbia orbited the Moon while Armstrong and Aldrin descended to the lunar surface in the lunar module, Eagle. After their moonwalk, the crew reunited in Columbia for the journey back to Earth.