When Preparing A Form, What Does Checkbox Imply?

When preparing a form as new or from a file, what does checking "This document requires signatures" imply? If I don't check it, I can add a signature box. When I check it, it seems to imply I can check a more complex signature box. There seem to be a few different elements too. But, is there a link that explains what this choice means in detail? Could someone explain it to me? Searching doesn't seem to yield anything. Results get overwhelmed by form creation hits.