They were called "parking" lights/lamps to differentiate them from driving lights. As has been posted in other threads on the same subject, it is illegal in many places (states and countries) to drive a vehicle with the parking lights on by themselves. It is however usually legal (and sometimes required) for parking lamps and driving lamps to be on at the same time.
The purpose of these lamps is/was to give indication that a vehicle with a running engine was parking/standing (not driving).
Wikipedia
