Backstory is defined as what happened to your characters before page one of the novel. It is the history leading up to the beginning of your book. New writers are told not to include too much backstory in their novels because it has a tendency to bog down the intensity of their prose.
I’ve heard it said that understanding when to insert backstory into a novel could be explained by thinking of it as metal filings and their attraction to a magnet.
Another use of backstory is in the developmental editing and revision of your novel. I recently discovered that there were deep secrets I needed to get across about my protagonist’s history. These secrets were things that had shaped his life up until the point where the novel started. This is the backstory.
I spent some time brainstorming how to include these snippets without slowing down the narrative of the novel. This morning I was updating my outline. Something I do after every new draft and I began a new timeline of the years that events in the backstory began. As I wrote down the dates and the events the answers to my brainstorming took root.
I now have the answer to where the backstory will do its most good. In this current manuscript I initially wrote over 150 pages of backstory about the lives of the father and son who are the dominant characters in the novel. One character loses his life at the beginning, and the other spends the entire novel trying to solve that crime.