Photographers sometimes printed photos on postcard stock rather than on photographic paper. The subjects of the photo then had a covenient way to send the image to family.
Here is a such a postcard photo:
Southwestern Lithuania, about 1910. Members of the family of Mr. Irene's maternal Grandmother, Anna, sent this snapshot to their immigrant daughters. The older woman wear babushkas, and there is a priest standing on the far right.