If you as organizer choose these fields, e.g. "company", "position" or "address" to be updated by your recipients during the reply process.
If you prefill these fields with content then your recipients will see this info on their reply page and will be able to edit it.
If you do not prefill these fields with data, then your recipients will see empty fields and will have to option to fill out these fields.
You can make them mandatory fields if you wish on your reply page.