Is your concern a question of what they are or do you have a car and might seek to remove them?
As noted, standard on the fancier trim levels and optional on others. Chrysler began using the fender-mounted turn signal repeaters in 1965 C-bodies as they were more in the driver's normal line of sight, rather than having to look at the instrument cluster to see if the signals were working. Which is why they normally didn't install bulbs in the instrument cluster sockets for the tiurn signal indicators, many times.
In some respects, it was a dress-up item as the prior "gun sights" that used to appear on upscale model front fenders and hoods, but with a practical and safety-related orientation.
Enjoy!
CBODY67