postcard
postcard
Noun
pl: postcards
Postcards are primarily associated with travel and nostalgia, serving as a physical memento of a location. While digital communication has reduced their frequency, they maintain a specific social ritual of "sending a postcard" to notify others of one's wellbeing and presence in a distant place.
In a linguistic context, the term refers specifically to the physical card. Because it is designed to be sent without an envelope, it implies a level of public visibility for the message, which distinguishes it from a traditional letter.