Details of the story outside of the chronological storyline are provided to the audience, often as a memory.
A flashback is an interruption in the plot to tell about something that has happened in the past, usually a memory, that can help the audience better understand a character or event. For example, if the main character is afraid of going to the hospital, the story may flashback to a time the character went to the hospital to say goodbye to his dying grandfather. The audience now understands that the character associates hospitals with death rather than wellness.
