Due to some deadlines and an upcoming vacation, I'm a bit behind on my slush. It will probably be a week or two for me to get caught up. We try hard here to keep our response times low, but life does run away from us at times. We really appreciate your patience.
Nathan Bransford has a great post on conflict right now. Go on and read it--now if you like. We'll wait.
Nathan makes some great points, especially that bit about rooting for Duke. But we here at Electric Spec think of conflict slightly differently, though it might be more our vernacular than actual meaning. We tend to label conflict internal and external. Nathan also failed to discuss obstacles, and how they play in.
External conflicts, of course, are the forces (hopefully sentient!--more on that in a minute) that keep characters from their goal. Internal conflicts are more the thoughts and wants and needs and guilt and past that often get between characters and their goals. I tend to think of internal conflict as "characters getting in their own way." I tend to think of external conflict more as "plot". No question we see a lot of external conflict and less internal conflict in our slushpile, but internal is what rounds out strories and characters, making them become fully realized and, well, real.
Sometimes I see stories in which the writer confuses "obstacles" for conflict. I think it's easiest to think of it this way. The difference lays in the goals: a storm's goal is not to stop the Company from getting the ring to Mordor. But the Ringwraiths' goal is just that. The storm creates an obstacle. The Ringwraiths create conflict.
In the opening scene of one of my novels, two brothers are arguing about how to go about searching for their missing mother. That's external conflict, and a bit of internal, as well, because past hurts, doubt, and guilt play into their exchange. Then they realize someone is following them. That's conflict, too. She's an antagonist, and antagonists always fall into the conflict camp. But as one of the characters tries to get away from her, he runs into friends who want to chat, a love interest, bad weather, and finally a gate which traps him in an alley. Those are examples of obstacles, even though some of them are clearly sentient.
I would argue every good story needs internal conflict, external conflict, and obstacles, but sometimes I notice one or another missing in stories in our slush. Maybe people don't think short stories need all this. But each are important in their own way. External conflict drives a story, it's the blood pumping through the heart. Internal conflict provides valuable insight into character. Obstacles can often serve double duty as world building tools.