A Hidden Field is used when you would like to have a notifier on the form for administrative recipients only instead of making it visible to your users. It is usually used as reference numbers or identifications. For example, you may have many forms named “Contact Form” for placing them on different websites. You can use the Hidden field on the form to label their embedded websites, so that you can know where the submission is coming from when you receive an email notification. The "Hidden" field properties may be set once the field is clicked on.
Field Label: This property is the text placed next to the form field that describes the type of data you want visitors to input.
Default Value: By setting this value, the field will be pre-populated with the text you enter.
Field ID: This property is a unique value assigned to a specific field. It can be used in conjunction with dynamic tokens to insert entry data to customize the AutoResponder confirmation message. Note: This value is assigned after a form has been saved.
Once you set the field options, please do not forget to click "Save Form" to save your work.