I am new to this so I probably have a dumb question, but I see quite a few people use plastic containers with lids like the one in your picture what exactly is that for? Is it a hide
It is a "moist hide". You put in dampened paper towels, coco fiber, etc for the Leo to get in to hide and the moisture also helps them shed their skin and if it is a gravid (pregnant) female a place to lay her eggs. If you have a hatchling or juvenile Leo you should only use the dampened paper towels... No loose substrate.
BTW, there are no dumb questions here. We are all here to learn and help each other. Even in instances where we may have differing opinions on something I have yet to see any rudeness or flaming. So ask away.