The outline structure of the document as described in Document Structure, forms the basis for defining sections of the exported document.
However, since the outline structure is also used for (for example) lists of
tasks, only the first three outline levels will be used as headings. Deeper
levels will become itemized lists. You can change the location of this
switch globally by setting the variable
org-export-headline-levels, or on a
per-file basis with a line