As for your first question,
When created in non-volcanic areas, water becomes heated as it comes into contact with hot rocks within the earth's crust. Then the water will rise back up to create hot springs. The volcanic activity responsible for creating the hot springs are caused by the moving hot spot, which is currently under Yellowstone.
As for your second question,
Balneology is the practice of treating and preventing disease through the use of natural mineral hot springs water. That's a use of hot springs.
