Answer:
Radioactivity is typically a high-energy wave that passes through cells and causes damage to them. However, there are different types, and they have very different effects on our body.
First, we have alpha particles. They're the biggest of all the types of radiation particles, therefore lacking the energy and speed to penetrate your skin, and typically won't do much damage from outside your body. Inside you body, however, it will wreak havoc on your sensitive tissues, and cause severe damage to cells and DNA. These situations typically happen in unfortunate events where a person inhales or swallows an alpha-emitter.
Next, we have beta particles. These are typically smaller than alpha particles, and hence have more speed. They can penetrate skin and get into our body but are typically less damaging to our inside tissues due to their ionization being weaker than those of alpha particles. They can also typically be stopped by a layer of clothing or a thin sheet of aluminum, but be prepared for some damage if the beta particles get inside your body through inhaling beta-emitters, for example.
Coming up are gamma rays, which are packets of energy like photons that are similar to visible light but have much, much higher energy. These are typically known as the most dangerous of radioactivity, due to their energy that will absolutely rip apart and destroy DNA or cells, and their incredible penetrative energy that will take at least a few meters of dense materials like lead or even concrete to stop.
Finally, we have X-rays. Similar to gamma rays, they are also little photons that act like visible light but have a lower energy than gamma rays, hence having less penetrative power. They are most known for their uses in medicine in X-ray scans to see the insides of a patient, or for their uses in CT scans to diagnose patients.
Hope this helped!