Wiktionary
n. (context literary English) In literary theory, meanings that are alluded to, above or beyond the printed text; interpretations of text.
Wikipedia
Paratext is a concept in literary interpretation. The main text of published authors (e.g. the story, non-fiction description, poems, etc.) is often surrounded by other material supplied by editors, printers, and publishers, which is known as the paratext. These added elements form a frame for the main text, and can change the reception of a text or its interpretation by the public. Paratext is most often associated with books, as they typically include a cover (with associated cover art), title, front matter (dedication, opening information, foreword), back matter (endpapers, colophon) footnotes, and many other materials not crafted by the author. Other editorial decisions can also fall into the category of paratext, such as the formatting or typography. Because of their close association with the text, it may seem that authors should be given the final say about paratextual materials, but often that is not the case. One example of controversy surrounding paratext is the case of the 2009 young adult novel Liar, which was initially published with an image of a white girl on the cover, although the narrator of the story was identified in the text as black.
The concept of paratext is closely related to the concept of hypotext, which is the earlier text that serves as a source for the current text.