What is the difference between psychiatrist, psychologist, therapist, counselor, social worker, etc? I know a psychiatrist can prescribe meds and the rest can't but I don't understand the granularity with each.

And I know every situation is different but what is discussed at these sessions?

I hate to group all medical professionals together, but I'm hesitant to spend more money to have another professional tell me..."no caffeine, alcohol, junk food; get exercise, get plenty of sleep, lower stress; etc." I'm doing all these thinks already.