So when you walk outside and into the sun, you're exposed to radiation, we need sunlight exposure to live, so again bringing up the parents comments regarding the need for "practical" advice.
By radiation here it is meant ionizing radiation, which comes in 3 major forms (exceptions do exist):
1- Alpha radiation: Basically helium atoms. Pretty harmless on the outside of your body, really really bad if inside your body. Do not eat/inhale.
2- Beta radiation: Electrons. Harmfulness varies, kinda. Stay away from it.
3- Gamma radiation: Likely what you're thinking of. These are photons. Harmfulness increases with frequency/energy of photon, mostly. Think X-rays, not UVa radiation.
Aside: UVa/b isn't ionizing, it just so happens to be the same wavelength as the short channel of your DNA strand and has a small, but noticeable, chance of breaking up your DNA. The biology of a sunburn is somewhat complicated, so please research on your own. Wear sunscreen and you're fine. With ionizing radiation you need to wear a lot of lead to be fine.
Other forms of harm exist for every known particle, but you'd need to stand right inside of the LHC to experience it or be cosmically unlucky (for say, neutrino based ionizing radiation).
My understanding is you actually need to wear sunscreen that blocks UVb and a lot doesn't. Which is why Zinc is preferred in places like Australia, because it actually "blocks" UVa/UVb, does'nt just stop you from getting red skin, it protects your DNA from radiation.
