what is this switch for?

y'all gotta bear with me, somethings that are passe' is new to me being a B/RB & 727 dude my whole life. I pulled this trans (engine too) out of a 88 5th Ave to go into a Duster. What is this switch for in the photo? Do I need to cut the pigtail off of the harness on the car it came on? If so what am I supposed to do with it? :-D