Every dealer I went to had a different answer and google isn't helping much either.

With a push button start, you're given a pair of smart keys.
In the dash, there's a port for the smart key.

What, exactly, is the purpose of the port and what does it do?

Thanks.

In the event that the smart key does not work properly or just simply runs out of battery you can unlock the car manually using the actual key and once you are inside the car you would go ahead and place the key in the port and the car will recognize it and charge they key while you drive.