what are nerf bars for atv

I’ve been seeing a lot of ATV riders use nerf bars, but I’m not entirely sure what their purpose is. I know they’re some kind of protection or accessory, but how exactly do they benefit riders and their ATVs?

Are they mainly for safety, performance, or aesthetics? Do nerf bars help with stability or prevent damage in any way? Also, are there different types or materials for them, and how do I choose the best ones for my ATV?

Looking forward to hearing your thoughts and experiences!