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.

: Receiving a postcard can make a person feel "closer" to the sender. It is a "touch from the heart" that can even outlast the sender, as seen in historical research where decades-old postcards provide a "vivid image" of past lives and social sentiments. Traditional Structure of a Postcard Postcard

If you are looking to write one yourself, standard postcard etiquette involves specific elements: Temporary Talismans « Kenyon Review Blog : A postcard carries the "authenticity of presence"