What's the difference between Chicago Style and Turabian?
The Chicago Manual of Style is often used in the social sciences and humanities. In addition to citation styles, there is also useful information on grammar and writing style, so it can be useful to actually look at the print manual.
Turabian refers to A Manual for Writers of Research Papers, Theses, and Dissertations, and is a simplified version of the Chicago Manual of Style used by researchers everywhere. If your instructor does not specify a style guide, this is the one we recommend that you use.
Notes-Bibliography vs. Author-Date
Notes-Bibliography style in Chicago is a style characterized by footnotes at the bottom of each page, and superscript numbers taking the place of in-text citation. The sources are reproduced in a bibliography at the end of the paper. Footnotes are intended to be read while the reader is going through the text, and the bibliography is used as a repository of potentially useful sources.
Author-Date style in Chicago is very similar to APA style. It uses in text citations at the end of sentences in parenthesis, which are intended to refer the reader to the source on the references page.
This guide to Chicago Style from the OWL at Purdue explains the Notes Bibliography style for Chicago and shows examples for formatting a research paper and its citations. It also has a brief section on Author Date style.