What is letter-card?

A letter-card is a type of postcard that is also used as a letter. It features a combination of a written message and a design on one side, with space for an address and postage on the other. Letter-cards were first introduced in the late 19th century as a way for people to send a quick message without the formality of a full letter. They were popular during the early 20th century, but their usage declined as the popularity of traditional postcards and letters increased. Nowadays, letter-cards are mostly used for formal correspondence or sending short messages. They are also commonly used in business settings as they provide a professional format for sending letters without the need for a separate envelope.