The body text of an assignment is the running text, i.e. the content.
The body text should be coherent and make sense on its own – even if you provide additional information in your notes, include figures, etc. See the entry on indents and sections.
The information about formalities is written in collaboration between Center for Educational Development (CED) and AU Library and is general guidelines for formal requirements. They do not replace the provisions in your academic regulations, your lecturers' guidance or information on your course's website. If in doubt ask your supervisor.