According to Johns Hopkins Medicine, a CT scan shows body parts such as organs, bones, fat and muscle in greater detail than a usual X-ray can provide. A CT scan does use X-rays, but the beam circles the area to be scanned and allows for more views and angles.
Johns Hopkins Medicine explains that contrast is a technique sometimes used in CT scans. With the substance taken either intravenously or orally, contrast makes a particular area of the body show up better on the scan. People might need to abstain from food before their CT scans; they should follow their doctor's' instructions.