Aren't they pretty much the same actually? Conflict/Tension? The terms seem to be used the same way and they can actually be synonymous, but...
Um, no. Conflict is when a character makes his or her presence known in a scene with a goal and is immediately confronted by an obstacle. That's great and it's necessary to hold the reader's interest. We all confront obstacles in our lives, we all need to understand how to face them, to overcome them. The reader can identify.
Okay, got that?
Now, tension is what evokes emotion in your reader. You know, that hair-standing-up-on-the-back-of-your-neck and the squirmy feeling in your stomach and the jittery, gotta-do-something feeling. That's the kind of stuff you want to make your reader feel. Those are the kinds of things that gets your readers involved with your story and will keep them reading until the end...and then want to pick up another book you've written.
So, Conflict and Tension have a sort of symbiotic relationship. Conflict should create tension, but unfortunately it doesn't always.
That in mind, how do we writers ratchet up the tension? What's the magic formula?
Well, I wouldn't call it magic and I sure wouldn't call it a formula, but here it is. Make your stakes high. Give your reader something to relate to, a struggle everyone can relate to and make sure you offer a clear conflict.
Conflict can be huge and in your face like a car chase, a martial arts battle or it can be a much more low key event like a clear break between two people with opposing desires. Whatever way you play it, make sure the conflict is there. If it isn't, rewrite, rewrite!
Oh, and with all this conflict and tension, pay attention to your characters. Are their responses clear and emotional in themselves? You need to know your characters inside-out. How they would respond. What would bring on the volcanic emotional eruption you need to keep your story snapping.