Brain cells die off, and as a result muscles no longer get the message to move. Everything slowly grinds to a halt. You walk less, blink less, swallow less, until you breathe less and die. Often an infection or pneumonia sets in earlier and kills you. That's what happened to my father.
Medication can lessen the symptoms.
Nothing stops it. Researchers have identified a Parkinson's gene. My family is at the center of the study. A search into our European roots has shown that it existed in previous generations also. We didn't know.