It is possible to display form data in emails which are sent out.

For example, this could be used as a registrant identifier for people signing up to take part in an event. If you combined this with taking a payment via the form, then the form ID would in effect be a Booking Reference. (see example uses of forms for Selling Tickets)

Form Response ID

This is the unique number given to each form response. You can show this in an email by adding in the following tag:  {id} 

Input Fields

You can display any form input field in an email using the following tag: {input_field_1} where 1 is the id of the input field you want to display

Finding Input Field Names

You can find the input field number by hovering over the input field name of the form within admin.