As screenwriters we’re taught that for a character to be multi-dimensional we often need to create a sufficient backstory to him or her so that the audience has a clearer picture to understand the character’s behavior, motivations, etc. Backstory gives the audience information about a character before your story begins, typically through the use of dialogue, flashbacks, or prologue. But like most elements of screenwriting care should be taken to balance “telling” with “showing”.
Review the discussions found in the following 2 articles:
Then try to explore examples from films where backstory is used in any of its forms and where it may be over-utilized, needed, or even absent.