'Míng xìn piàn' literally combines three characters: 'míng' (bright, clear), 'xìn' (letter, message), and 'piàn' (sheet, piece). Though 'míng' might suggest 'clear' or 'bright', in this compound it historically refers to 'public' or 'open' — reflecting the original function of postcards as messages written openly on a single sheet, without an envelope. Thus, 'míng xìn piàn' means a lightweight, rectangular card designed for writing short messages and mailing without enclosure.

This word is used exclusively for standard postal postcards — often with a picture on one side and space for address and message on the other. It's common in travel contexts (e.g., sending from scenic locations), tourism, and language learning exchanges. Unlike letters (xìn), postcards are informal, quick, and economical, making them ideal for brief greetings or updates during trips.