A literature review is a comprehensive and up-to-date overview of the principal research about the topic being studied.
A Literature Review Is Not:
So, what is it then?
A literature review is an integrated analysis-- not just a summary-- of scholarly writings that are related directly to your research question. That is, it represents the literature that provides background information on your topic and shows a correspondence between those writings 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.