While you work on 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 the changes straight away or unpublish the link to make it unavailable to public.
All options can be found within the form editor by selecting the dropdown arrow in the top right of the form editor header.
Here you'll see the three options and a short description on what will happen when they're selected.
You can see when changes have been made to a form but not yet published by the button in the top right saying Publish changes instead of Published.