Citation, Documentation of Sources

Q. I am using Chicago style for the first time. I am totally confused! Can you explain to me when to use footnotes (which my professor wants at the end of the paper) and when to use a bibliography? I am under the impression that she wants both used for this particular paper, and I can’t figure out how to distinguish when to use each. Help!

A. Notes (which are called “footnotes” when they appear at the bottom of the page and “endnotes” when they are collected at the end of the paper) tell the reader exactly where they can verify something that you wrote. As you write your paper, each time you quote something or use a fact that you borrowed from an article or book, create a note that includes the author, the title, and the page number of that source. A bibliography is more general, and you can pull it together after you finish writing your paper. It lists in alphabetical order (by the authors’ last names) all the sources you read for your research, whether or not you mentioned them in your paper or in the notes. Bibliography entries give complete information for each source: author, title, city of publication, publisher, and date. A note can give less information, since the reader can look in the bibliography for the full citation. If your professor wants full information to appear in both places, include the exact page number only in the note. You can omit page numbers from the bibliography, because its purpose is to list works as a whole. If a bibliography item is a single article in a journal or a chapter in a book, however, you should give the range of pages for that article or chapter in order to help the reader find it in the larger work. You can find examples of how to cite various sources at our Citation Quick Guide.

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]