The Stone Granary is a storage unit that will be able to keep your supplies together and organized, so your supplies aren't scattered everywhere. It's suggested to make the granary organized by item and not to put random items inside of them. The Stone Granary is the same thing as the Wood Granary but non-flammable, and since stone is pretty easy to obtain. This structure is recommended over the wood granary, since it is raid resistant due to being not-flammable. Its also strongly recommended to build multiple granary's if you have many items.