When you save a page you've just edited, it saves as a draft. It is not publicly available on your website unless you "Publish" it or "Save and Publish" it. This means that visitors will see the page without the latest changes, and you have a chance to keep working on changing it further. In Composite C1, you can view the "saved"/ "unpublished" page as well as preview the page while editing without actually saving it...