Why don't I find a site on Internet that explains what items are for?

[Iscah]

But that was NOT how this discussion began, it began with there not being any explanation online, that I can easily find, that explains what a chest (in FFXIV) is for.

I think you're going about things the wrong way here.

You're starting from the assumption that "chests" must exist, therefore you go looking for information about chests and assume that an item called a chest must be the inventory solution you are searching for. If you can't find any information about chests (or skinning monsters), it must be that nobody is explaining how to use them.

That's not actually how it works.

We don't have storage chests, therefore there is no reason for anyone to explain how to use them. And people aren't going to provide detailed information about what features are not in a game, or not by a particular term, because that list could be infinite. No wiki or item database is going to explain where you can get something that isn't there.

If you've bought a "stack of three chests" then you must have Splintered Chests. It's a crafting ingredient for a housing item.

Inventory is, basically, a notorious mess here. They made deeply-embedded poor decisions when setting up their database that have become a problem as the game increased. They can't expand the main inventory so keep working around it with segmented things.

Your main inventory, retainers and saddlebag are the entirety of standard item storage available to you. You also have the glamour dresser at the inn for storing gear you only want to keep for its appearance, and if you have a house or apartment then there is a furniture storeroom but it can't be used for other types of items. If you're in an FC there is a shared company chest.

(And no, if you ever see it and get excited, the "storage bench" furniture item is not actually storage. That's just flavour text.)