Subplots, up to this point, had always been all of the drama going on OUTSIDE of a book that kept me from finishing said book. Whether I was reading or writing.
However. I will echo KAK's appreciation of James's post because given the levels of complication I seem determined to pack into a single novel, I'm well acquainted with subplots. I just didn't know it.
It was from that standpoint that I'd been approaching subplots - that a subplot was a storyline that ran in parallel with my main story, but that didn't directly involve my main character(s). If that definition holds, I don't currently do subplots. I have my hands too full of ALL THE THINGS going on in my main plot. Hey. Do you think I could shoehorn this kitchen sink into the conflict?
But if James's definition of backstory = unresolved conflict feeding current drive = story thread to be resolved (or failed) in parallel with main story action, well then I'm there. That said, though, I'd like to try plotting in a secondary character's story. Just to see if I can pull it off.