What is the difference between “Commemorative” and “Definitive” stamps?

Definitive stamps are also known as regular-issue stamps. They pay postage on everyday mail and are issued in a lot of denominations. Often a particular definitive stamp design is used for long periods of time, and sometimes reprinted to replenish supplies. A Commemorative is a stamp issued to honor an important person, event, or anniversary. It’s printed in smaller quantities than definitives, and is sold for a limited time, usually a few months. Unsold stamps are generally destroyed. Click here to read more about these types of stamps and see some examples.