redearslider.com

been a bit curious and started asking myself questions:

what does a filter even do, why don't I know....

Okay,
Can someone tell me what it does? Suck up poop or clean the water.
If possible, could you like, put a detailed answer



Second, is eating their poop fine? Because the second they see poop, they race to it and eat it.

This should answer your first question.
http://www.firsttankguide.net/filters.php

And yes it's ok if they eat their own poop.

Okay, good to know that my knowledge is perfectly fine.

Another thing, I see some white translucent scute shaped things, my turtles are recovering from a shell fungus, could this be the fungus peeling off?

Fungus infected scutes are usually opaque white. Translucent scutes that have been shed are normal.