A literature review is an integrated analysis-- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question. That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.
A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment. Rely heavily on the guidelines your instructor has given you.
Why is it important?
A literature review is important because it:
Your literature review should be guided by your central research question. the literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.
How many studies do you need to look at? How comprehensive should it be? How many years should it cover?
Some questions to help you analyze the research: