Paratext

A term coined by critic Gérard Genette to describe the portions of a text conceptualized as extrinsic to the text proper. Paratexts include prefatory elements (prefaces, acknowledgments, introductions, title pages), supplementary or concluding elements (footnotes or endnotes, conclusions, appendices), and elements which facilitate the use of the text (tables of contents, indices, page numbers, chapter or section headings, marginal notes, running titles) or increase its aesthetic appeal (borders, illustrations, decorative or historiated letters).

From Folgerpedia.