This video demonstrates how a user with the "Author" role can create content, create new revisions and move the content to the "Needs Review" state, but not publish the content.

Creating content

I'll login as "Author" and create a new article. I'll select the "Exhibits" section, and you'll see that the default moderation state is "Draft" as per the Article content type settings. Because I can move content to the "Needs Review" state, I could also choose that here as well, but I'll leave it as Draft, and save the content.