What is the name of the ball thing on the back of your truck called? You hook your trailer to it?

So I hate that my car has LED daytime running lights but halogen bulbs I think it looks awful. I was wondering how simple it is to change to LEDs and what kind of LEDs I would need...

I replaced my struts on my 99 Camry which ran in perfect condition. Now you can feel every little bump driving down the street...