Ionizing radiation consists of particles or waves with enough energy to strip off the outer electrons of the atoms they encounter, thereby changing an electrically-neutral atom into an ion.  Non-Ionizing radiation hasn't enough energy to strip electrons off; however, it imparts enough energy to cause the atom to vibrate, resulting in heating. Radiation in the range of 1 Hertz to 300 Gigahertz is considered Non-Ionizing, and includes the low end of ultraviolet and visible light (the Sun is a source of UV light.) However, because Non-Ionizing radiation increases heat, exposure can lead to burns, as anyone who's spent too much time at the beach can attest.  Ionizing radiation includes high end ultraviolet to x-rays and cosmic rays, all above 300 Gigahertz.  Because it creates ions, Ionizing radiation can create free-radical molecules, which can damage DNA.