“Ionization” is a process by which electrons are stripped from atoms and molecules. This process can produce molecular changes that can lead to damage in biological tissue, including effects on DNA,genetic material. This process requires interaction with high levels of electromagnetic energy. Those types of electromagnetic radiation with enough energy to ionize biological material include X-radiation and gamma radiation. Therefore, X-rays and gamma rays are examples of ionizing radiation.
The energy levels associated with RF and microwave radiation, on the other hand, are not great enough to cause the ionization of atoms and molecules and RF energy is, therefore, is a type of non-ionizing radiation.
Other types of non-ionizing radiation include visible light, infrared radiation and other forms of electromagnetic radiation with relatively low frequencies.
Often the term “radiation” is used to apply to ionizing radiation such as that associated with nuclear power plants. Ionizing radiation should not be confused with the nuclear radiation lower-energy to non-ionizing, radiation with respect to possible biological effects, since the mechanisms of action are quite different