What is a footnote?

A footnote can reference to a particular book, article, web page etc at a chosen point in your essay or dissertation. You may provide a footnote to refer to 

• a single quote
• a single page or range of pages
• a chapter
• an entire book, article etc

A footnote is typically a numbered bibliographic reference in a smaller font size at the end of a page, possibly including a page number or range of pages e.g.

¹ McInnes, C. (2002). Fatal Attraction? Air Power and the West. Contemporary Security Policy, 22(3), 28-51.
² Gat, A. (2001). A History of Military Thought: from the Enlightenment to the Cold War. New York: Oxford University Press.

which is in turn referred to by a number (also in superscript) in the appropriate place in the page.

A copy of the full bibliographic reference (usually omitting page references) is sometimes also included in the bibliography at the end of the work.