Style
No matter what the style, all citations have several pieces in common:
The style used - APA, MLA, Chicago, etc. - depends on the discipline and what the professor requires. Style guides inform the citation style and sometimes the format of your paper.
When in doubt, ask your professor.
Confused about the difference between MLA, APA, and Chicago styles?
This chart from Purdue OWL shows a comparison of these three styles and how they differ for most types of sources.