Corner card (philately)

A corner card is a special type of stamp that has information in one of the corners to show where the letter or package is coming from. It's like a little address label on the stamp! Philately is a fancy word for stamp collecting. People who collect stamps like to look for corner cards because they can tell them interesting things about where the letter came from and when it was sent. So, a corner card is a cool stamp that helps stamp collectors keep track of where letters and packages come from.