2.8 Footnotes

A footnote is defined in a paragraph that is started by a footnote marker in square brackets in column 0, no indentation allowed. The footnote reference is simply the marker in square brackets, inside text. For example:

     The Org homepage[fn:1] now looks a lot better than it used to.
     ...
     [fn:1] The link is: http://orgmode.org

The following commands handle footnotes:

C-c C-x f

The footnote action command. When the cursor is on a footnote reference, jump to the definition. When it is at a definition, jump to the (first) reference. Otherwise, create a new footnote. When this command is called with a prefix argument, a menu of additional options including renumbering is offered.

C-c C-c

Jump between definition and reference.

Further reading
Chapter 2 of the manual
Sacha Chua's tutorial