Postcards are rectangular-shaped dual sided pieces of thick paper that are used for mailings without the need to utilize an envelope. The modern incarnation of the postcard usually includes a picture or other image on one side of the card, with space reserved for a mailing address, postage, and a message on the opposite side. They are routinely used for a wide range of personal and business purposes and tend to be more cost-effective than mailing letters through a national postal system.