Backstory does the same thing for characters. It takes them from one-dimensional, to multi-faceted, well rounded, I-wanna-meet-this-person heroes and heroines.
Backstory is the backbone of your story. Without a backbone, what would the human body do? If you don't know the answer to that, research it out. You will be amazed at what we would look like without a backbone. And please remember that the same concept applies to your writing. More specifically, your characters.
We end our segment on Backstory with a Q&A. You ask the questions and I'll answer them. If no one asks a question then I'll pout.