Visible light and x-ray radiation are similar in that they are both composed of photons traveling in waves, but differ in the frequency and energy of the waves. The electromagnetic spectrum is made up of several different types of radiation. From highest energy to lowest energy they are: Gamma rays, x-rays, ultraviolet light, visible light, infrared light, microwaves and radio waves. The first three are what are called ionizing radiation. That is, the waves are so energetic that they can actually interact with and possibly destroy or alter DNA molecules in cells. This can result in the destruction of the cell, the organ or the creation of mutant forms of the DNA we call cancer. Hence, if you receive too many sunburns (caused by ultraviolet light from the sun), you may eventually get skin cancer. However, visible light, infrared light, microwaves and radio waves have such low energy that the waves are unable to interact with DNA and therefore have no effect on cell reproduction.
So in summary, all these types of radiation (x-ray, visible light, radio wave, etc.) are, in their basic form, the same thing. They are “packets” of photons that travel in waves. However, what makes them different is the frequency and wavelength of those waves (which is in itself a function of the amount of energy in the wave).
Having gone back and read the previous two paragraphs, I realized that I made x-rays seem like pretty scary and damaging things. In reality they are not. Not only does modern x-ray equipment use relatively little radiation to obtain a radiograph, but also, believe it or not, your body is mostly made up of open space, which the x-rays pass right through. Your body is also composed of lots of water and minerals (e.g. calcium) which are unaffected by x-ray radiation. While it’s obvious you don’t want to be exposed unnecessarily to x-rays, almost always the benefits outweigh the risks when getting an x-ray image.
I hope this answered the reader’s question and has helped you get a basic understanding of x-ray radiation, at least in its relationship to visible light and other radiation types on the Electromagnetic spectrum.