If you want, you can hide a field from a form. This can be done by enabling the "Hide question" toggle under settings. Once the change is published, the field is then hidden and wont be shown to users filling out the form.
This feature is particularly useful when you might want to hide certain questions from the form temporarily without deleting the question, since deleting a question will also delete all the responses for that question.
Hidden fields can also be used for Tracking UTM parameters or for that matter any kind of information that you already have by using it in conjunction with the pre-fillinf form fields with URL parameters feature.