An Extra is a person who works  in the background on a TV show, in a Movie or perhaps a Commercial.
	The purpose of having Extras is to make the scene more realistic and believable to the viewer.
	For example, imagine a restaurant scene in a Movie where the main Actors are talking over dinner - it would look very strange if there was no-one else in the restaurant wouldn't it? That's where Extras come in to fill up the background and add some atmosphere to the scene.
	Extras can play passer's-by in a street scene, shoppers and lots more different roles. Sometimes an Extra might be required to wear special clothes such as a Police  or Nurse's uniform. Don't worry, the Wardrobe people are there to cater for any special requirements like that!
	Extras aren't required to speak or do any proper acting, but sometimes they might have to perform a little, just to make things look right, like maybe pretending to talk to each other in the background or perhaps looking as if they are shopping for something.
	The main thing is that once the Extras are in place, the scene looks much more real!