Have you ever had to have a conversation explaining death with a NK?

Don't currently need advice, but I'm just curious. My 3.5yo NK talks about animals or people being "dead" sometimes in play and such, but she doesn't understand yet what death actually is. I'm very curious what being "dead" means in her brain.

I HAVE had that conversation 3x in the past with kids (because they bring it up) and it seems like the understanding of death, realizing they will one day die, their parents will die, etc. sinks in around age 4-5.