so the dip bar at my gym is like V i see people doing it towards the back where it is more narrow and towards the front where it is wider ? my question is what is the difference does it hit something more or harder ?
When it comes to dips, play it by feel. If you want to put more emphasis on the chest, lean forward until you feel the chest doing more work. If you're wanting to hit the triceps hard, keep the back straight and make sure you're feeling the triceps doing a lot of work.
Dips are great because you can change it up during the exercise.
You want to perform a dip at a grip width where your elbows are point nearly straight back and your hands are like 3'' wider than your waist. This will cause your upper arms to stay tight to your body and the exact spot is different for everyone. The V bar is to accommodate everyones body size in one set.
Anywhere else on the bar is essentially a different exercise. The wider the grip, the more it is like a fly. I tend to think that you should do 90% standard form/grip in exercises. For instance, I wide grip bench press or squat with a power stance or sumo deadlift only once in a while but do the standard exercises every week.