Shortened note
Also called: short form note, short citation
The abbreviated footnote used for a source you have already cited in full: author surname, a short title, and the page.
Chicago's preferred way to cite a source for the second and later times is a shortened note rather than ibid. It carries the author's last name, a shortened form of the title (four words or fewer, keeping the distinctive part), and the locator.
Because it repeats enough to be identifiable on its own, a shortened note survives editing and re-ordering, and it works for a reader who has opened the book in the middle. That robustness is exactly why the 17th edition demoted ibid.
Chicago, first note then shortened
1. Amara Okafor, The Craft of Research Writing, 2nd ed. (Cambridge: University Press, 2019), 88. → 4. Okafor, Craft of Research Writing, 112.