Postcard -

: A postcard carries the "authenticity of presence". The physical card was once in the hands of the sender at the very location pictured, making it a "little splinter" of the ordinary that can eventually transition into the realm of the historical.

If you are looking to write one yourself, standard postcard etiquette involves specific elements: Temporary Talismans « Kenyon Review Blog Postcard

The postcard is more than a simple souvenir; it is a that bridges the gap between the sender’s immediate experience and the recipient’s distant world. Unlike instantaneous digital messages, a postcard represents a deliberate act of choosing a specific image and hand-writing a message, often focusing on a single "key idea or feeling". The Enduring Power of the Postcard : A postcard carries the "authenticity of presence"