Note, some portions of answers to previous and related questions (What do you call a quote from an article that is displayed prominently in the article itself? and What are footnotes called when they aren’t in the footer?) are included below.
Two of the main terms for [a prominently displayed quote] are callout and pull quote, the former meaning “A pull quote: an excerpt from an article (such as in a news magazine) that is duplicated in a large font alongside the article so as to grab a reader’s attention and indicate the article’s topic”, and the latter “In newspaper and magazine publishing, a brief excerpt drawn from an article and used out of context.”
Related terms [...] include sidebar, “a short news story printed alongside a larger one” or “information placed at the side of a webpage”; hook in the sense “A brief, punchy opening statement intended to draw the reader or viewer into a book or play”; and blurb, “A short description of a book, film, musical work, or other product written and used for promotional purposes.” Like callouts, box quotes, or pull quotes, these items may appear in large bright type to attract attention. [jwpat7]
Sidenotes is a common term used to denote the notes, trivia or anything interesting noted by the author on the sidelines of pages of his book. [Mohit]
Marginalia, see Wikipedia: Marginalia or margin note. [Dohn Joe]
The terms marginal notes, marginal markings, graffiti, and graffito are used to refer to the numerous small sidebars in italics within Concrete Mathematics by Graham, Knuth, and Patashnik. [jwpat7]
You might use the word annotations to describe explanatory text or comments found on the margins of literary works and diagrams. [KeyBrd Basher]
