What is the difference between prednisone and naproxyen for a dislocated shoulder. What does each one do. Why am I taking them?

Ask the doctor. Prednisone and naprosyn (naproxen) are both antiinflammatory agents. Prednisone is a corticosteroid while naprosyn (naproxen) is a nonsteroidal agent. Why don't you just ask the doctor who prescribed them why they are used together. I generally do not prescribed them at the same time.
Be careful here... A dislocated shoulder is painful, i'm sure. Prenisone is an anti-inflammatory medication, and so is naproxen. Both are used to reduce swelling, inflammation, and pain related to inflammation. My concern is that both medications can be irritating to the stomach. The combination could prove to be too much and may cause gastrointestinal ulcers and/or bleeding. Call your doctor and ask him/her.