A draft is a version of a page or blog post with changes that haven’t yet been published.
If you want to edit an already published page, but don’t want to publish the changes yet, click “Close” at the bottom right of the page to leave the editor.
You will see the “Close editor” dialog which tells you that you made changes that have not been published yet. If you click on “Discard all changes”, your unpublished changes will be deleted. If you click “Keep draft”, your changes will be saved in a draft.
Please also check this question in this forum.
Please watch our Video #79 of the Video Tutorial Series “Learn Atlassian Confluence” and review this information of Atlassian’s documentation.