How can I determine what information is shown in the email?

For example, I would like any text to be included in the email results. Not just the form answers.

By default the headers, text fields are not included in the notification emails. You'll be able to add only the fields from the form to the notifications. However, the email composer is a full editor that allows to you to insert graphics, create tables, etc. The headers or text on your JotForm can be copied and pasted here in the email content.

You may also want to refer to the following guide that the submission can be included with the text and headers.

http://www.jotform.com/help/305-How-to-show-headers-or-text-for-contracts-terms-agreements-in-the-PDF-format-of-a-submission

So that you can place a PDF link on your email notification as well.