An X-ray photograph of a person's lungs.

X-radiation is a kind of electromagnetic radiation. X-rays are waves of X-radiation. They have a shorter wavelength, and therefore more energy, than ultraviolet radiation. X-rays have a much shorter wavelength than visible light (the light that we can see). Radiation with shorter wavelengths (more energy) than the X-ray is called Gamma radiation (γ-rays). These are all parts of the electromagnetic spectrum.