While editing your forms, you may want to keep a version in draft to return to at a later stage before publishing. Alternatively, you may want to publish any changes straight away, or unpublish to make a form unavailable to the public.
All of these options are available within the form editor. Just select the dropdown arrow in the top right of the form editor header, and you'll see the three options along with a short description for each of them.
You can see when changes have been made to a form but not yet published by selecting the top right Publish changes button, instead of the Published button.
This status is also indicated on the forms table by the 'information' icon. You can hover over this icon to check if there are unpublished changes on the form.