system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is it that our bodies do when we sleep? Why do we need it, what is "replenished" etc?
gpt
We don't really have a definite answer, some say it's important in the conversion of short term to long term memory, that when you sleep your mind basically gets a chance to"De-fragment" all of the information you took in that day.

Others say it's necessary in order to give our bodies time to heal and recover, but our bodies are constantly healing and generating new tissue, while sleep may make the process easier it's not as if our bodies only heal while we're asleep.

Some scientists believe it's something living organisms simply adapted to do as a way to conserve energy, we can't hunt or gather food when our vision at night is poor, so it would make sense to go dormant as a survival mechanism in order to not waste energy.

It could be one of these, it could all of them, or something we don't even know, but at this point the jury is still out.

Sleep is necessary to us, but why we and many living organism developed this nessecity is still unknown.

*Edit some typos.