The Nativity refers to the story of the birth of Jesus as recorded in the Bible where He was visited by Wise Men from the East who had been following the Bethlehem Star and from shepards nearby who were visited by a host of angels. Jesus himself was in a manger in a stable or cave with Mary and Joseph.
The recreation of nativity scenes has been popular in Christian culture, especially around Christmas time. The scenes usually have three wise men, although this is not stated in the text, only that they brought three gifts. Also, it is believed the wise men would not have arrived until later, but they are still included in traditional nativity scenes.
While Nativity scenes have been a proud part of American heritage, in recent years they have often been found unconstitutional when displayed on public lands, an unfortunate part of the times.