This image shows a group of people, possibly a family, as they ride horses provided by the local stable owner. Such horse rentals were very common in mid-20th century United States, as it provided an experience which was fast disappearing for many urban families.
The description on the back of the card states simply:
CK-310 Greetings from Hart, Michigan
—Hart, Michigan is located in west central Michigan, and the county it is the seat of has a coastline of Lake Michigan. It is a small town in a rural county, and such entertainments as this were provided for summer tourists and visitors.
This image likely dates from the 1950s.