Humid hides?

[MissterDog]

Can someone explain humid hides to me and if and when they are necessary? Is it used only when your bp sheds or is it there all the time? I've heard of people using moss, but cautioned to make sure the bp doesn't stay in all the time to prevent belly rot? Which side should you put it in?

I've also heard of two humid hides used, one hot and one cold in additional to the regular hides. Is there such a thing as too many hides?

I know I can always try making my own, but I admit I kinda really like how these hides look;
https://www.amazon.com/dp/B000HHLQJU...F8GF75NU&psc=1

Would that that be a decent humid hide if I put moss in it? Also where do you guys get your moss from?

Thanks!