X-ray (radiography) is the most frequently performed radiology procedure.
X-rays are part of the electromagnetic spectrum and have an extremely short wavelength, or high frequency, making them high energy. This means they can penetrate most materials and can be used to examine the body 'structure'. They are most useful for bony structures in the body but do show some soft tissue (non bony areas) detail as well.
An x-ray image (radiograph) is produced on a photosensitive plate when the x-ray beam passes through your body. The parts of your body appear light or dark due to the different rates that your tissues absorb the X-rays. Calcium in bones absorbs X-rays the most, so bones look white on the radiograph. Fat and other soft tissues absorb less, and look gray. Air absorbs least, so lungs look black. X-rays are two-dimensional images and therefore several images at different angles may be required to make an accurate diagnosis.