To cite sources successfully, it's crucial you have a clear understanding of:
The TYPE of source you're using (magazine article vs. book vs. reference book article)
The PLACE where you found that source (in print at the library vs. online via a database vs. online via a Web site).
The source's full "bibliographic information" (authors/editors, title, edition, publisher, pages, etc.)
The citation style you use will affect your paper in three places:
The general format of the paper. This includes margins, font, page numbers, line spacing, titles, headings, etc.
The bibliography. The bibliography is the cumulative list of all sources used in your research. In MLA, this is called the Works Cited list; in APA it's called References, and in Chicago it's called Reference List.
In-text citation. Citing sources within the body of your paper let's your reader know you are incorporating someone else's words/research/ideas.
Created by the Modern Language Association, MLA is most often used by the Humanities, which includes languages, literature, philosophy, visual & performing arts.