Topic summary
Frame narrative

Extracted from the Wikipedia article Frame story.
A frame story (also known as a frame tale, framing device, frame narrative, sandwich narrative, nested narrative, or intercalation) is the literary technique and narrative structure in which an opening narrative introduces either a more emphasized second narrative or a set of shorter tales. The frame story leads readers from a first story into one or more other in-depth stories within it. In other words, a frame story is the use of one or more stories-within-a-story across the majority of a narrative's content, where the inner story is the main one: the one with the most detail.