Apollo 12 was the second mission in which humans walked on the lunar surface and returned to Earth. On 19 November 1969 two astronauts (Apollo 12 Commander Charles P. "Pete" Conrad and LM Pilot Alan L. Bean) landed in Oceanus Procellarum (Ocean of Storms) on the Moon in the Lunar Module (LM) while the Command and Service Module (CSM) (with CM pilot Richard F. Gordon) continued in lunar orbit. During their stay on the Moon, the astronauts set up scientific experiments, took photographs, examined the nearby Surveyor 3 spacecraft which had landed on the Moon 2 1/2 years earlier and removed pieces for later examination on Earth, and collected lunar samples on two moonwalk EVA's. The LM took off from the Moon on 20 November and the astronauts returned to Earth on 24 November.
References
http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1969-099A