The function of a literature review is to address the previous research that has been done on a particular subject. This previous research serves as a foundation for you to develop your own unique hypothesis. One of the motivations for conducting a literature review is to ensure the argument you plan to present has not been presented before. This page includes techniques for finding articles for your literature review, as well as an explanation of "peer reviewed," or "scholarly," works.
For an in-depth explanation of the writing process for a literature review, check out this webpage from the University of North Carolina - Chapel Hill's Writing Center.
There are several ways to go about finding articles for your literature review. It's a good idea to try each approach so that you get a well-rounded view of the subject area you are researching.