This picture says it all—it’s a snapshot into history. Backstory is information given about something that happened in the story’s past.
It often helps readers know a little more about a situation, and it lets writers tell instead of show (though backstory doesn’t necessarily have to be tell). Bear in mind that good writing is neither all tell nor all show, but strikes a balance in between.
A few ways to convey backstory are verb tenses, key words, thoughts, dialogue and flashbacks.
Need some examples?
These examples are found at the bottom of my article How to Develop Voice.
Dean didn’t know the milk had turned until the first swig—for after a terrible accident three years ago, his nose no longer detected the spoiled stench of rotting food.
I stood at the edge of the darkened forest, peering inside. My body hesitated before squeezing between the pines and oaks… What sounded like The Necrofaire howled in the distance, hungry to kill again. Why did I let them talk me into believing this was a good idea?
The MC’s thought (the question) is backstory if readers didn’t see her friends dare her.
Another example is,
And then there’s Ben. My best friend since the second grade.
If dialogue is used to convey backstory, it should be purposeful and move the plot forward. (Do NOT use “As you know, Bob,” dialogue).
“Chan, you knew I’d broken my back, why would you say I was faking?”
“As you know, Bob, your wife has two kids.”
Flashbacks can show backstory rather than tell it. Only use flashbacks if they work.
Basically, backstory lets you know about something that happened before the plot of the novel takes place. If the novel is in present tense, the backstory is (usually) in past. If the novel is in past tense, the backstory is (usually) in past perfect. It can be shown with flashbacks, revealed through dialogue, exposed in thoughts or attached to key words like originally, when, another, before… My examples’ key words are after, no longer, again and since.
Backstory has its place, it adds dimension to the characters and their relationships, it solidifies certain events, and is quite integral to most works. It can be overdone, but is a powerful tool when used properly.