The moral of "The Emperor's New Clothes" is that people should be willing to speak up if they know the truth, even if they think that everyone else will laugh at them. Another possible moral of the story is that people should not believe things without empirical evidence. A third moral is that children speak the truth.
In "The Emperor's New Clothes" by Hans Christen Andersen, a couple of swindlers pretending to be weavers make a special suit for an emperor. They tell the emperor and his followers that the clothes are invisible to people who are too stupid for their jobs. No one can see the clothing, but no one wants to admit this fact because they do not want to be identified as foolish.
In an older version of the tale, it was said that a person couldn't see the clothing if he was not really the child of his father. Afraid to be identified as illegitimate, the people in this version also pretended that they could see the clothing. Andersen reportedly read some of the earlier versions of the tale, but he decided to change the premise of which type of people could not see the clothing.
At the end of the story, a child is the one to point out the truth. Slowly, all of the people in the kingdom admit that they cannot see the clothing, and the truth about the weavers is revealed.