It exposes the person to somewhat more radiation than a standard X-ray. Therefore, doctors use it only when they need to see internal movement. One use is to observe the lungs and diaphragm. The diaphragm is the muscle between the chest and the abdomen. It controls breathing.
Fluoroscopy shows whether it moves properly.
It can also show various parts of the digestive tract. Barium swallow and barium enema tests both use it. Contrast dyes allow views of the gall bladder, bile ducts, and pancreas. Another test inspects the enclosed space around the spinal column. Finally, it may be used to guide the passage of catheters or other tools through the body.