Postcards are a type of mail that are typically smaller than regular envelopes and have a picture or design on one side. Postcards are usually sent through the mail without an envelope, and the message is written on the back of the card. Postcards are often used as a means of communication for personal or business purposes, such as sending greetings or promoting a product or service. They can also be collected as a hobby, with some postcards being valued for their historical or artistic significance. In addition to traditional physical postcards, it is also possible to send digital postcards through the internet or other electronic means.