This image depicts one of the miracles of Gautama Buddha, in which he replicated himself so that every person present had him to converse with.  This miracle was performed as part of a competition with a group of non-Buddhists who had challenged him.  These competitions with a king as a judge were common in ancient India.  The Buddha performed this miracle under a mango tree, which he miraculously made appear.  Gautama Buddha (the historical Buddha) is usually distinguished from other buddhas by his plain dress.