The bite splints are made to relax your jaw muscles/joints, and reduce some clenching (it can't get rid of your clenching because clenching happens naturally to everybody) They also provide a measure of protection for the teeth. You will always clench on your splint but it will be reduced in time and prevent more injury to your already injured muscles/joints. Do you know what I mean?
There are different splints made according to your tmjd type. My is just to relax my jaw muscles and joints and reduce clenching. I still clench after wearing the bite plate for 8 years or so. Some splints are used to reposition the jaw, but these are used for people who may have joint problems, and they are meant to change your bite. I don't know a whole alot about the different kinds of splints... maybe somebody else on the board might know more about it.
I hope I have answered some of your questions.