All are men from the United States of America who traveled to the Moon as part of NASA's Apollo program during the period from December 1968 to December 1972.
Apart from these 24 people, no human being has ever left earth orbit (with a height of a few hundred km); they have thus gone farther from the earth than anyone else has ever gone (see "where no man has gone before").
As of 2003, only the following twelve people have walked on the Moon, each on one mission only. Nobody has walked on the moon since 1972.
On each of the (first listed) missions above one astronaut orbited the moon while the other two landed. In addition each of missions Apollo 8, Apollo 10 and Apollo 13 had a three man crew and closely encountered the moon (entering orbit in the case of the former two missions, while Apollo 13 only passed around it). Thus 12 more people have been close to the moon:
People who have walked on the moon
People who have encountered the moon closely without landing