The Chicago Manual of Style (17th ed.) provides standardized rules for formatting a paper (margins, line spacing, etc.), as well as a consistent method for citing ideas, quotations, facts, and paraphrases borrowed from other sources.
Chicago style provides two different methods for source citation.
Notes-Bibliography style uses footnotes (or endnotes) for citations within the text and a bibliography at the end. This format is used in History, Art, and other humanities disciplines.
Author-Date style uses parenthetical references for in-text citations and a reference list at the end. This format is used in many science and social science disciplines.