REAL PHOTO POSTCARD (RPPC)
An actual photograph printed on postcard-sized paper and printed on the reverse for use as a postcard.
These can be unique, or nearly so, as seen in the first example image showing a view of a little-observed event from the first World War, or they can be often-reproduced images for sale to tourists, as seen in the second example image showing two different postcards of a man climbing a coconut tree.
These cards may be postally used as seen in the first image, or retained as keepsakes as seen in the second image. The photographs are generally black and white, but they might be hand-colored as seen in the second image.