X-rays are are electromagnetic waves which penetrate many materials to varying degrees. An X-ray machine is essentially a camera which uses X-rays instead of visible light to expose the film. X-rays are often the first tools doctors use to diagnose illness so that treatment can begin.
Since tissue, fat, muscle, tumors, bones, and other masses absorb X-rays at different levels, doctors can quickly determine the condition of the internal organs and skeletal structure in order to make crucial decisions. They can also use modified X-ray procedures to examine softer tissue, such as the lungs, blood vessels, or intestines.