If you have an ANALOG television, you need a converter. Only low power and Class A television stations are still able to broadcast over the air in analog. Everyone else converted to digital months ago.
If you have a newer TV with a built in digital tuner,. you don't need a box.
I had a converter box and an antenna and it did NOT bring in anything. I called the closest tv station to ask wtf and the engineer there said without an outside antenna there is no way I can get service bc of the distance between my apt and the closest tv tower. Outside antenna is not an option in my apt. So I threw the stupid converter box and antenna in the trash even though they were new. Good thing I can watch tv and movies online and thank goodness for Netflix.