When I say people, I mean your characters (for you writers.) My characters become so real to me as I'm writing them, they are like real people...real friends. Hmm...does this mean I'm a grownup with imaginary friends? Could be, but at least I don't talk to them. Aloud. But they do talk to me, in my head. They talk to each other more and I get to listen in like a sneaky eavesdropper. They usually tell about their pasts at some point in the story.
A character's past is the much maligned backstory that everyone thinks is the kiss of death. It isn't. Only the "backstory dump" is the bad thing. Very bad. No one wants to read a chapter about what happened during the course of your character's past up to this point. That would be boring. Start your story in the here and now on that day when everything changes. Give out teaspoons of info on important events from your character's past here and there through the story. Important events are also called Backstory Events. These are things that changed the course of the character's life. Big, traumatizing, interesting things. They serve as motivation (fuel) for what drives the character now toward what he or she wants (or avoids.) That's why you can't leave out backstory alltogether.
Here's a link to the first (ever) article I wrote a couple years ago about backstory. This is a pdf download of a whole newsletter. My article, Backstory Success, is on page 8. If you're a writer who struggles with where, when or how to use backstory you might find this helpful.