Hi AD,
Attribute only (Checked) : Means that particular Infoobject we can add to ODS however we cannot see in output and BEx designer and not available for navigation like drill down/up, variable creation, restriction etc.
Attribute only (unchecked): Available for display, navigation and others.
Hope you understand, still if any doubts, please go through the documentation, for clear idea.
Thank you,
Nanda