Any idea or quote from other people or resources that you use in writing your paper needs to be cited. Citations give credit to those people/resources and provide your reader with the information needed to identify your sources.
A citation of a book generally includes author(s), title, publisher and date. A citation of an article generally includes author(s), article title, journal title, volume, pages, and date. Citations for web documents and articles from databases also include a URL and may need the date the information was accessed.
There are many different formats used in writing papers. The American Psychological Association (APA), and Modern Language Association (MLA), University of Chicago (Chicago) and the American Sociological Association (ASA) are some of the most popular. Always check with your professor to know which format or style should be used.