Part of which makes characters believable are their background stories. It is the component that makes readers love or hate them. Any character devoid of their own what, when, why, who, where, and how becomes unrealistic and forgettable. But in fiction, too much of anything could spoil narration. A character’s background story, if written with too much information, would produce its own book as a fictional biography. An effective narration conveying character history must be brief and should not interfere with the story’s pacing. Daniel Defoe’s Moll Flanders is a good example of how a character’s background story is told briefly enough for readers to understand the protagonist and how she connects to the present. 

This story within your story is information that conveys experiences and events within the passage of time. Consider this story: A young man has been assimilated early into the mafia.

The background: (a) The young man was abandoned by his parents when he was a child (b) He becomes a petty thief in the streets of Cosa Nostra (c) He steals a wallet from a man who happens to be the boss of the local mafia (d) The mafia boss takes pity on the boy and adopts him (e) The boy is sent to school and learns the ropes about the underground world (f) As a young man, he takes on his first mob assignment as a loan shark. 

All these events are necessary to establish the shaping and motivation of the character. Each of the stages in the young man’s life could well be written in detail, but it would require lots of pages that might bog down the pacing. A more effective way to dramatize these events is through quick narration.

Example: In his early growing years, Calvino never had it easy. At the age of eight, he was abandoned by his parents--his father left him for another woman, while his mother ran away with a plumber. Forced to live on the streets, he became a petty thief in the streets of Sicily. One fateful day, he snagged the wallet of a well-dressed, aging gentleman, who, having keen senses developed from years of dealing with thugs, grabbed young Calvino’s hand. After minutes of begging and imploring, Calvino’s life took a turn as the man, who turned out to be the infamous Don Flavio Luchesi, adopted the young Calvino. Soon, Calvino was attending school and getting acquainted with the rudiments of underground mafia operations. He assumed the task of loan-sharking for Don Flavio and worked his way up.

The events in the life of Calvino are grouped together into a single paragraph that illustrates his early beginnings in the mafia. The reader gains a quick glimpse but a full understanding of the character’s social, emotional, and psychological formation without having to feel they are reading a grocery list. The writer succeeds in injecting this passage without creating what feels like an unnecessary interruption in the middle of his narrative. This technique applies to background stories of places and even animals as well.