Students sometimes think that citations are necessary only when using material that is a direct quote. This is not true. A citation is necessary any time you include any information or idea that is not, yours (that is, directly or indirectly derived from someone else's thinking or writing). Any non-original idea that you fail to cite is plagiarized. Plagiarism is stealing. It can result in your failing the course!
The purpose of citations is to permit other researchers to locate the sources used. It is important to make them complete and understandable. For every source, include the title author(s), and date. For books, note publisher and place of publication. For articles, note the name of Journal, volume number, issue number, and page numbers.
All references should be identified at the appropriate point in the text by the last name of the author, year of publication, and page number where needed. Identify subsequent citations of the same source the same way as the first.
Citing your sources has several specific benefits for you the student. Of course, a primary benefit is that it shows you are crediting your sources and so avoiding the possibility of plagiarizing. Even more important though is that it gives you credit. It is concrete documentation of the hard work you have done in researching the background of your topic including the ideas other people have had on the subject. Professors generally respect and reward well-researched papers.
Attribution, at its most basic level, requires that you include a bibliographic citation for each source that you use.
Typical elements in bibliographic citations from the print publication world include.
Depending on the material type:
What type of material did your source come from? A different material types have different citation elements so "what" to record can differ from source to source.
Where was it published?
Where did you find it?
When was it published?
Did it appear in a particular edition of a larger work? What are the details of the particular edition?
Did you access it on a particular date?