Shops are one of the more interactive functions Boundless Universe has to offer its members. From here you can spend your hard earned gold to purchase various items. Some of these items are actually usable and expire when used, causing you to buy them again at some point. Shops can open and close, and even be stolen from.
Some items grant effects. Some items have a use limit. Quite frankly, you can't shoot a 6-shooter 8 times without refilling it with bullets... same applies to other stocks. Can't eat the same apple twice... unless you regurgitate it for some reason...
Shops do not have unlimited inventory. It is very possible for them to sell out of an item. It will be up to the shopkeeps or workers to restock.
Shops aren't necessarily 24/7. They can be closed by descretion of the owner... but that doesn't mean you can't take what you need anyway. Lockpicks are an item you can use to take a chance at being a sneaky sneaky thief you are. Careful though, just because you're sneaky doesn't mean the act won't be found out.