Since nobody has answered your questions so far, it’s an aftermarket badge that some Model 3 and Model Y owners put in their car to further spell out which trim they have
P - Performance Model
3/Y - Car Model
D - Dual Motor
+/- - + signifies the performance upgrade package is equipped (red calipers, CF spoiler, lowered suspension) whereas the - represents the performance models without the performance upgrade package.
Hope that helps.