This is the internal housing of a shark-fin car antenna (also called a roof-mounted shark fin antenna or aerial module).
Key features visible:
Black plastic outer shell shaped like a shark fin (common on modern cars for a sleek look).
Open underside showing the hollow interior.
Small green circuit board (PCB) fixed with two screws.
Twisted copper wire antenna element connected to the board, ending in a small connector/LED-style tip.
Mounting points and screw holes for attaching to the car roof.
Purpose
These antennas typically combine several functions in one unit:
AM/FM radio reception
GPS
Cellular / telematics (for connected car features)