A synopsis is a very brief summary of the story line of the film or book you are writing about. In essay writing, it helps the person reading your essay by setting out the background of your ideas and the context of the story.
EXAMPLES
The Help is set in 1960's Mississippi at a time when the Jim Crow laws caused segregation between black and white people. The story follows a white woman called Skeeter in her bid to encourage black maids to share their stories. As a result of her efforts, she loses lifelong friendships and grows in confidence whilst the bigoted townspeople of Jackson find themselves at risk of nationwide embarrassment.