A postage stamp is a small piece of paper that is affixed to a letter or package to indicate that postage has been paid. It typically features a design, such as a portrait, symbol, or artwork, and has a specific value printed on it. Postage stamps are used in mail systems around the world to facilitate the delivery of mail. When a stamp is purchased, it allows the sender to send their item through the postal service, such as the United States Postal Service or Royal Mail. Stamps can be collected as a hobby, known as philately, where enthusiasts gather and study different designs and historical significance.