Overview: Documentation Systems
Research writing is how an academic community exchanges ideas and shares the results of their work. You may hear this community called a "discourse community". That's because its members belong to a specific discipline, like anthropology, Victorian literature or physics. The ongoing conversation between members of these communities helps further the work of individual contributors.
Publishing is one of the ways in which these communities talk to each other: text-books, articles in professional journals and conference proceedings, for example, are part of the conversation. Collectively, they constitute a library of sources upon which any researcher may draw. To "borrow" from this library, participants in the conversation must document their use of these sources.
Available to meet this requirement are a variety of documentation systems designed to fit the specific needs of different academic disciplines. In the humanities, for instance, the Modern Language Association (MLA) style is preferred, while in the social and natural sciences there is a larger tendency toward the American Psychological Association (APA) style.
There are no hard and fast rules, however. The Chicago Manual of Style (CMS) is often used in both the humanities and the social sciences. In the "hard sciences" preferences run more to the Council of Biology Editors (CBE) style and the Civil Engineering Citation Guide (CEC). Your instructors will advise you on which to use.