Use the word any when you're talking about every possible quantity of something — whether it's one, a few, or many. You might ask an ice cream truck driver, "Do you have any ice cream sandwiches?"
Any refers to non-specific amounts of something, as when you ask your friend, "Do you have any advice about what movie I should see?" or you ask a bakery worker, "Do you have any chocolate croissants left?" It also means "at all," like when you complain, "That pep talk didn't make me feel any better." In Old English, the word was ænig, which meant both "any" and "anyone," or literally, "one-y."