An item is one thing, usually in a group or a list. At a restaurant, you might find yourself interested in a particular item on the menu (until you notice the price and decide to order a hamburger instead).
Item is a Latin word meaning “likewise.” As early as the 15th century, this word was used in formal writing to introduce each point in a list (like a medieval version of the bullet point). The meaning of item has continued to evolve. Since the 1970s, it’s been used in casual speech to refer to a romantically involved couple: "Brad and Angelina — they're a hot item!"