A body double is a person who works in the movie or television production industry. Body doubles are models that act in scenes that actors or actresses do not want to do. For example, body doubles sometimes act in love scenes or scenes of nudity, where a person's body is shown.
Body doubles are usually models that have developed very good bodies by exercising and by eating well. Actors whose characters must appear nude or otherwise show more skin, often have flaws and imperfections such as may come with age or being overweight and it can be expensive to digitally edit these out. Often, movies or television shows that use body doubles do not admit that a body double model was used.
In the popular American movie Pretty Woman, a fashion and parts model named Donna Scoggins posed for the infamous movie poster in thigh-high boots, while another body double, Shelley Michelle, filmed nude scenes that actress Julia Roberts did not want to do. 
Another job in the movie and television production industry where people do actions that the actors or actresses do not want to do is the job of stuntman. A stuntman is a person who does dangerous actions in movies, for example, jumping, falling, getting in a car accident, or pretending to fight with knives.
What distinguishes a "stunt person" from a "stunt double" is the particular character they portray. If the character in question is a main character and/or central to the plot and uniquely identifiable, the stuntman is then typically referred to as a "stunt double" in the credits.
- Double take: behind every 'Pretty Woman' stands a prettier woman, a superfit body double to the stars American Fitness, July-August, 1992 by Michael Loprete http://126.96.36.199/search?q=cache:atj9-A8DVX0J:www.findarticles.com/p/articles/mi_m0675/is_n4_v10/ai_12448376+body+double&hl=en&ct=clnk&cd=14
- IMDb.com, "Pretty Woman" cast credits, https://www.imdb.com/title/tt0100405/combined