X-rays are invisible electromagnetic waves that we send through the body to produce images of internal tissues, bones, and organs on film for diagnostic purposes. When the body is X -rayed, different densities of the body allow varying amounts of the X-ray beams to pass through. The rays that pass through the body are then absorbed by detector plates that produce a "negative" type picture (the more solid a structure is, the whiter it appears on the film). The soft tissues in the body (such as blood, skin, fat, and muscle) allow most of the X-ray to pass through and appear dark gray on the film or digital media.  The sinuses are usually filled with air, which appears black on X-ray film. Alternatively, bone or a tumor allows few of the X-rays to pass through and appears white on the X-ray. When there is a break in a bone, the X-ray beam passes through the broken area and appears as a dark line in the white bone.

Standard X-rays are performed for many reasons. They can obtain basic information regarding the size, shape, and position of organs. X-rays of the extremities may also be used to evaluate bone growth and development in children. The advantages of an X-ray are that it is simple, quick, noninvasive, relatively inexpensive, and can give the doctor useful information. However, a disadvantage is that an X-ray can determine only that a problem exists, not the specific cause of the problem. X-ray technology is used in other types of diagnostic procedures, such as computed tomography (CT) scans and fluoroscopy.