Custom Mapping

I have a question. I know if we put in the standard shortcode, the basic fields get mapped automatically. If we were to do the short code and add one custom field into it, does it still send the standard ones and in addition the custom one?

Or will it just send the specific one that you are put in the short code.

I just want to know if we have to put all the standard ones into the short code mapping along with the custom ones to get all of it working.

Thanks