To say this fully: It means that this particular hub is not featured. It will not be indexed for Google, and it will not show up on the HubPages pages showing hubs people might read. At the default setting (which is best for your own income) it will also not show up on your own profile page.
And the reason it will not show up is because the hub was read and was seen to be of low quality. The solution is to go to the Learning Center and read about the elements that make a quality hub, and revise your hub. When you finish editing, it will go through the review process again.