Collins did not set foot on our satellite because its mission consisted of stay in orbit around the Moon and wait the return of Aldrin and Armstrong, who Yes descended to the surface of the star.
While Aldrin and Armstrong were collecting lunar soil samples and performed a series of experiments on the surface of the Moon, Collins obligation was to pilot the command, in orbit around the moon module. The command module was the small ship that had traveled from the Earth to the Moon and that it would have to return to our planet from the moon.
From the command module had separated the capsule that had been transported to Aldrin and Armstrong until the surface of the Moon, and the command module should return once completed the Mission of both astronauts.
Michael Collins was educated at the Military Academy of West Point and was a fighter pilot before being elected as a NASA astronaut, in 1963.
Before participating in the Apollo project, it had formed part of the Gemini project and had piloted the ship Gemini X, flight in which managed to successfully two outputs to the space, suitably protected by a space suit.
After participating in the Apolo XI he left the astronaut Corps, was devoted to the history of space flight, and became director of the Smithsonian air museum and the Washington area.